mm_mol_suppmat. 72KB Jun 05 2011 09:30:46 PM
Supplementary Section
The Dipole Moments of acyl halides. The dipole moments of acyl halides are
given in Table S1.
Table S1
Molecular Structures of the larger acyl halides. For n-butyryl halides, 2methylpropionyl bromide, and the 2,2-dimethylpropionyl halides, no experimentally
determined molecular structures have been reported. Therefore, theoretically calculated
structures (rg bond lengths were converted from the corresponding re bond lengths for all
ab initio calculations) were used for comparison purposes. For n-butyryl fluoride and 2,2dimethylpropionyl fluoride, the molecular structures from ab initio RHF/6-31G* level
calculations were scaled by comparing the rg structure19 and the re structure (ab initio
RHF/6-31G* method) of acetyl fluoride.
For n-butyryl chloride and 2,2-dimethyl-
propionyl chloride, the molecular structures from ab initio RHF/6-31G* level calculations
were scaled by comparing the rg structure21 and re structure (ab initio RHF/6-31G*
method) of acetyl chloride. For n-butyryl bromide, 2-methylpropionyl bromide, and 2,2dimethylpropionyl bromide, the molecular structures from ab initio RHF/3-21G* level
calculations were scaled by comparing the rg structure21 and re structure (ab initio RHF/321G* method) of acetyl bromide.
The molecular structures for the n-butyryl halides are represented in Table S2.
Table S2
The calculated molecular structures of n-butyryl fluoride, n-butyryl chloride, and n-butyryl
bromide, compared to the scaled structures, gave rms differences of 0.001 Å and 0.51
degrees, 0.002 Å and 0.72 degrees, and 0.004 Å and 0.72 degrees, respectively, for the
bond lengths (excluding C-H bonds) and bond angles (excluding angles containing
hydrogen).
For 2-methylpropionyl fluoride, the experimentally determined r0 molecular
structure of the gauche conformations available from a microwave experiment.i The re
structure of the syn form obtained from an RHF/6-31G* calculation was converted to rg
structure. Both the experimental and ab initio geometries were compared to the MM3
structure. The molecular geometries for the 2-methylpropionyl halides are represented in
Table S3. The rms differences for the bond lengths (excluding C-H bonds) and bond
angles (excluding any angle containing hydrogen) were 0.008 Å and 0.6 degrees, and
0.002 Å and 0.7 degrees for the syn and the gauche forms, respectively. The MM3
derived molecular structure of 2-methylpropionyl chloride was also compared to the rg
structure from electron diffraction.iia
The calculated structure for 2-methylpropionyl
chloride gave an rms difference of 0.006 Å for the bond lengths (excluding C-H bonds).
The value of the angle ∠(C3-C2-C4) from the experiment is too big, compared to either
our calculated value or to the ab initio value, and gave a 1.2 degrees rms deviation with
this angle excluded. The calculated molecular structures for the gauche and syn isomers
of 2-methylpropionyl bromide, compared to the molecular structures scaled as previously,
gave rms differences of 0.003 Å and 1.43 degrees, and 0.004 Å and 1.30 degrees,
respectively, for the bond lengths and bond angles.
Table S3
The molecular structures for the 2,2-dimethylpropionyl halides are shown in Table
S4. The calculated molecular structures of 2,2-dimethylpropionyl fluoride, chloride, and
Table S4
bromide, compared to the scaled structures, gave rms differences of 0.004 Å and 1.16
degrees, 0.003 Å and 1.68 degrees, and 0.005 Å and 1.42 degrees, respectively, for the
bond lengths (excluding C-H bonds) and bond angles (excluding any angle containing
hydrogen).
It was found that the C-X bond lengths in 2-methylpropionyl halides and 2,2dimethylpropionyl halides are increased, compared with the propionyl and n-butyryl
halides, which reflected the steric effects of the β-methyl groups.
Introducing an
additional methyl group in the β-position of propionyl fluoride gave no increase in the C-F
bond length from microwave studies,26a,40 but an approximately 0.003 Å increase in the CF bond length from our calculations and an approximately 0.001 Å increase according to
RHF/6-31G* calculations. The introduction of an additional methyl group in the βposition of propionyl chloride resulted in a 0.007 Å increase in the C-Cl bond length
according to electron diffraction studies,28,41a and approximately a 0.004 Å increase from
both ab initio quantum mechanics and molecular mechanics methods. Another methyl
group added to the β-position of propionyl bromide resulted in an approximately 0.004 Å
increase of the C-Br bond length with our calculations and a 0.003 Å increase from 321G* calculations.
Conformational analysis of the larger acyl halides. From the low resolution
microwave spectroscopy studies,iii it was reported that n-butyryl halides exist as syn-anti
(the first conformational symbol 'syn' for O=Cα-Cβ-Cγ torsional angle, and the second
symbol 'anti' for Cα-Cβ-Cγ-Cδ torsional angle) and syn-gauche conformers with roughly
the same energies. For n-butyryl fluoride, the less stable (about 0.3 kcal/mol) skew-anti
conformer was characterized. More precisely, our calculations on n-butyryl fluoride found
that the syn-gauche, skew-anti, skew-gauche, and gauche-gauche conformers have 849,
1222, and 1656 cal/mol, respectively, higher energies than the syn-anti conformer. The
corresponding energy values for n-butyryl chloride and bromide are 850, 1341, and 1784
cal/mol, and 844, 705, and 1090 cal/mol, respectively.
For the n-butyryl bromide,
interestingly the skew-anti form was more stable than the skew-gauche form.
Each
conformer of n-butyryl halides are compared in Table S5.
Table S5
From the torsional potential barriers of both acetyl fluoride and propionyl fluoride
from microwave studies, Stiefvater et al.27 in late 1960's predicted the conformations of 2methylpropionyl fluoride to be two equivalent optical isomers, gauche forms (one of
methyl group eclipsing the carbonyl group) and one syn conformer (the α-hydrogen
eclipsing the carbonyl group) with the gauche conformers being 1130 cal/mol (∆H0)
stable. Recently, Durig et al.40 determined an energy difference of 1320 cal/mol (∆H0)
from the temperature-dependent gas phase Raman spectrum. Our calculations showed
good agreement to the Stiefvater's predicted value27 and Durig's determined value40: the
gauche conformer was 1198 cal/mol (∆H0) or 1156 cal/mol (∆E0) more stable than the
syn. For 2-methylpropionyl chloride, our calculations showed that the gauche conformer
was 1609 cal/mol (∆H0) or 1693 cal/mol (∆E0) more stable than the syn. Our energy
difference was much higher than the value from a liquid Raman study41b (987 cal/mol,
∆H0), from electron diffraction study41a (700 cal/mol, ∆G0), or from ab initio MP2/631G* level calculation41a (910 cal/mol, ∆E0).
For 2-methylpropionyl bromide, our
molecular mechanics calculations showed that the gauche conformer was 672 cal/mol
(∆E0) or 759 cal/mol (∆H0) more stable than the syn conformer. The energy difference
between the stable conformers and other energy parameters for 2-methylpropionyl halides
are listed in Table S6.
Table S6
From the gas phase far-IR spectrum of 2,2-dimethylpropionyl fluoride and 2,2dimethylpropionyl chloride,34 the barriers to internal rotation have been determined to be
1755 cal/mol and 2307 cal/mol by applying the observed CC=O-C torsional fundamental
frequencies and Mathieu equation. From our calculations the barriers to internal rotation
are 1458 cal/mol and 2582 cal/mol for 2,2-dimethylpropionyl fluoride and chloride,
respectively.
Table S1. Dipole moments (in Debye) of acyl halides
(a) formyl fluoride
HCOF
exp.a
µtotal
2.02(4)
exp.b
Ab initioc
RHF/6-31G* MP2/6-31G*
1.99(3)
2.39
2.49
MM3
MM3 - exp.a
2.24
0.22
(b) formyl chloride
HCOCl
exp.d
µtotal
Ab initioc
RHF/6-31G* MP2/6-31G*
2.20
2.31
1.6(2)
MM3 - exp.d
MM3
2.25
0.65
(c) formyl bromide
HCOBr
µtotal
Ab initioe
RHF/3-21G*
2.17
MM3 - Ab initioe
MM3
2.23
0.06
(d) acetyl fluoride
CH3COF
exp.f
µtotal
Ab initioc
RHF/6-31G* MP2/6-31G*
3.09
3.26
2.96(3)
MM3
MM3 - exp.f
2.69
-0.27
(e) acetyl chloride
CH3COCl
exp.g
µtotal
2.713(8)
Ab initioc
RHF/6-31G* MP2/6-31G*
3.04
3.16
MM3
MM3 - exp.g
2.72
0.01
(f) acetyl bromide
CH3COBr
µtotal
Ab initioe
RHF/3-21G*
2.99
MM3
2.70
MM3-Ab initioe
-0.29
(g) propionyl fluoride
CH3CH2COF
exp.h
µtotal
s-trans
2.90(5)
gauche
3.08
Ab initioc
RHF/6-31G*
s-trans
gauche
3.10
3.25
MM3 - exp.h
MM3
s-trans
2.70
gauche
2.69
s-trans gauche
-0.20
-0.39
MM3
MM3 - exp.i
MM3 - Ab initioc
s-trans gauche
2.725
2.717
s-trans
0.10
(h) propionyl chloride
CH3CH2COCl
exp.i
µtotal
s-trans
2.63
Ab initioc
RHF/6-31G*
s-trans gauche
3.11
3.25
gauche
-0.53
(i) propionyl bromide
CH3CH2COBr
µtotal
Ab initioe
RHF/3-21G*
s-trans
gauche
3.02
3.18
MM3 - Ab initioe
MM3
s-trans
2.717
gauche
2.710
s-trans
-0.30
gauche
-0.47
(j) 2-methylpropionyl fluoride
(CH3)2CHCOF
exp.j
µtotal
gauche
2.98(1)
Ab initioc
RHF/6-31G*
gauche syn
3.18
3.32
MM3
gauche
2.699
syn
2.692
MM3 - exp.j
MM3 - Ab initioc
gauchec
-0.28
syn
-0.39
a)Taken from reference 17.
b)P. Favero and J. G. Baker, Nuovo Cimento, 17, 2942 (1960).
c)Using the Gaussian 90 program, in this work.
d)Taken from reference 18 a).
e)Using the Gaussian 94 program, in this work.
f)Taken from reference 20.
g)R. V. Galeev, L. N. Gunderova, A. H. Mamleev, and N. M. Pozdeev, Zh. Strukt. Khim., 36, 424 (1995).
h)Taken from reference 27.
i)G. T. Martin and J. R. Partington, J. Chem. Soc., 58, 158 (1936).
j)Taken from reference 40.
Table S2. Structural parameters (bond lengths in Å, and bond angles in degrees) of nbutyryl fluoride, n-butyryl chloride, and n-butyryl bromidea
(a) n-butyryl fluoride
CH3CH2CH2COF
r(C=O)
r(C-F)
r(C1-C2)c
r(C2-C3)
r(C3-C4)
r(C-H)av
∠(C-C=O)
∠(C-C-F)
∠(O=C-F)
∠(C1-C2-C3)
∠(C2-C3-C4)
∠(C-C-H)av
∠(H-C-H)av
∠(C-C-C=O)
rms deviationd
Calculated,rgb
1.186
1.363
1.510
--1.105
128.79
110.82
120.38
113.29
111.95
109.93
107.06
0.0
(bond length)
(bond angle)
MM3
1.1849
1.3640
1.5087
1.5207
1.5319
1.1121
129.315
110.101
120.584
112.743
112.381
109.910
107.163
0.0
MM3 - Calculatedb
-0.001
0.001
-0.001
--0.007
0.52
-0.72
0.20
-0.55
0.43
-0.02
0.10
0.0
0.001
0.51
MM3
1.1861
1.8017
1.5157
1.5276
1.5318
1.1124
127.484
111.702
120.814
112.713
112.344
109.906
107.187
0.0
MM3 - Calculatede
-0.001
0.000
0.003
--0.017
-0.07
-1.00
1.06
0.20
0.63
-0.15
0.03
0.0
0.002
0.72
(b)n-butyryl chloride
CH3CH2CH2COCl
r(C=O)
r(C-Cl)
r(C1-C2)c
r(C2-C3)
r(C3-C4)
r(C-H)av
∠(C-C=O)
∠(C-C-Cl)
∠(O=C-Cl)
∠(C1-C2-C3)
∠(C2-C3-C4)
∠(C-C-H)av
∠(H-C-H)av
∠(C-C-C=O)
rms deviationd
Calculated,rge
1.187
1.802
1.513
--1.095
127.55
112.70
119.75
112.51
111.71
110.05
107.15
0.0
(bond length)
(bond angle)
(c) n-butyryl bromide
CH3CH2CH2COBr
r(C=O)
r(C-Br)
r(C1-C2)c
r(C2-C3)
r(C3-C4)
r(C-H)av
∠(C-C=O)
∠(C-C-Br)
∠(O=C-Br)
∠(C1-C2-C3)
∠(C2-C3-C4)
∠(C-C-H)av
∠(H-C1-H)av
∠(C-C-C=O)
rms deviationd
Calculated,rgf
1.185
1.979
1.522
---127.67
111.56
120.77
111.65
111.09
109.87
107.77
0.0
(bond length)
(bond angle)
MM3
1.1833
1.9794
1.5161
1.5263
1.5318
1.1130
127.730
111.454
120.816
112.648
112.346
109.913
107.197
0.0
MM3 - Calculatedf
-0.002
0.000
-0.006
---0.06
-0.11
0.05
1.00
1.26
0.11
-0.57
0.0
0.004
0.72
a)Only the most stable syn-anti conformer is considered.
b)Converted from the re structure: (r(C=O) = 1.1691, r(C-F) = 1.3273, r(C1-C2) = 1.5005, r(C2-C3) =
1.5260, r(C3-C4) = 1.5275, and r(C-H)av = 1.0857) from ab initio RHF/6-31G* method (Gaussian 90
program, in this work). The scaling is done by comparing the rg structure from the electron diffraction
experiment (reference 19) and the re structure from ab initio RHF/6-31G* method of acetyl fluoride:
(rg(C=O) - re(C=O) = 0.017, rg(C-F) - re(C-F) = 0.036, rg(C-C(O)) - re(C-C(O)) = 0.009, and rg(C-H)av re(C-H)av = 0.019).
c)Numbering of carbons is C4-C3-C2-C1=O.
d)For the rms deviation of bond length, the C-H bond is excluded. For the rms deviation of bond angle,
any angle containing hydrogen is excluded.
e)Converted from the re structure: (r(C=O) = 1.1674, r(C-Cl) = 1.7889, r(C1-C2) = 1.5080, r(C2-C3) =
1.5275, r(C3-C4) = 1.5279, and r(C-H)av = 1.0854) from ab initio RHF/6-31G* method (Gaussian 90
program, in this work). The scaling is done by comparing the rg structure from the electron diffraction
experiment (reference 21) and the re structure from ab initio RHF/6-31G* method of acetyl chloride:
(rg(C=O) - re(C=O) = 0.020, rg(C-Cl) - re(C-Cl) = 0.013, rg(C-C(O)) - re(C-C(O)) = 0.005, and rg(C-H)av re(C-H)av = 0.010).
f)Converted from the re structure: (r(C=O) = 1.1866, r(C-Br) = 1.9551, r(C1-C2) = 1.5068, r(C2-C3) =
1.5360, r(C3-C4) = 1.5395, and r(C-H)av = 1.0839) from ab initio RHF/3-21G* method (Gaussian 94
program, in this work). For the scaling, see Table 3 (c).
Table S3. Structural parameters (bond lengths in Å, and bond angles in degrees) of 2methylpropionyl fluoride, 2-methylpropionyl chloride, and 2-methylpropionyl
bromide
(a) 2-methylpropionyl fluoride
(CH3)2CHCOF
Exp.,rga Calculated,rgb
gauche gauche syn
r(C=O)
1.184 1.187 1.187
r(C-F)
1.352 1.365 1.366
r(C1-C2)c
1.505 1.516 1.515
r(C2-C3)
1.539 --r(C2-C4)
1.529 --r(C2-H)
1.108 1.106 1.101
r(C-H)av(CH3)
1.104 1.103 1.103
128.7 128.82 128.37
∠(C-C=O)
111.3 111.14 111.64
∠(C-C-F)
120.0 120.04 119.99
∠(O=C-F)
110.4 109.84 110.20
∠(C1-C2-C3)
110.7 110.83 110.20
∠(C1-C2-C4)
110.0 112.45 110.95
∠(C3-C2-C4)
105.5 105.73 105.54
∠(C1-C2-H)
-108.86 -∠(C3,4-C2-H)av
∠(C2-C3,4-H)av(CH3) 110.6 110.71 110.73
-108.20 -∠(H-C-H)av(CH3)
118.5 118.5
0.0
∠(H-C2-C1=O)
d
rms deviation
(bond length)
(bond angle)
MM3
MM3 - Exp.,rga MM3 - Calc,rgb
gauche
syn
gauche
syn
1.1850 1.1849
0.001
-0.002
1.3675 1.3672
0.013
0.001
1.5139 1.5128
0.009
-0.002
1.5340 1.5339
-0.005
-1.5225 1.5339
-0.006
-1.1128 1.1088
0.005
0.008
1.1111 1.1110
0.007
0.008
129.090 128.431
0.39
0.06
110.383 110.770
-0.92
-0.87
120.518 120.799
0.52
0.81
111.124 111.125
0.72
0.93
111.238 111.125
0.54
0.93
110.087 110.525
0.09
0.43
107.655 107.584
2.16
2.04
108.309 108.171
--111.680 111.646
1.08
0.92
107.176 107.210
--119.4
0.0
0.9
0.0
0.008
0.59
0.002
0.75
(b) 2-methylpropionyl chloride
(CH3)2CHCOCl
ED.,rge
r(C=O)
1.186(3)
r(C-Cl)
1.804(4)
r(C1-C2)c
1.511(2)
r(C2-C3)
1.540(2)
r(C2-C4)
1.534(2)
r(C2-H)
1.088(6)
r(C-H)av(CH3)
1.108(6)
127.3(7)
∠(C-C=O)
113.6(5)
∠(C-C-Cl)
119.1
∠(O=C-Cl)
109.9(8)
∠(C1-C2-C3)
109.7(8)
∠(C1-C2-C4)
113.8(27)j
∠(C3-C2-C4)
106.8
∠(C1-C2-H)
-∠(C3,4-C2-H)av
∠(C2-C3,4-H)av(CH3) 111.7(18)
-∠(H-C-H)av(CH3)
h
130.1(37)
∠(H-C2-C1=O)
i
0.0
∠(H-C2-C1=O)
rms deviationd
(bond length)
(bond angle)
Ab initiof
gauche
syn
1.188
1.188
1.805
1.805
1.522
1.523
----1.094
1.094
1.094
1.094
127.16
126.13
113.54
114.86
119.30
119.01
109.78
111.60
109.74
111.60
111.97
112.19
106.87
103.09
109.19
108.95
110.50
110.73
108.24
108.18
136.1
0.0
MM3g
1.1863
1.8060
1.5219
1.5435
1.5305
1.1117
1.1109
127.052
112.235
120.694
110.997
111.011
109.581
108.430
108.338
111.677
108.332
131.9
0.0
MM3 - ED.,rge
0.000
0.002
0.011
0.004
-0.004
0.024
0.003
-0.25
-1.37
1.59
1.10
1.31
-4.22
1.63
-0.02
-1.8
0.0
0.006
1.22
(c) 2-methylpropionyl bromide
(CH3)2CHCOBr
Calculated,rgk
gauche
syn
1.185
1.185
1.983
1.986
1.528
1.530
--------127.66
127.30
112.16
113.36
120.18
119.34
109.00
110.76
109.28
110.76
111.06
111.54
107.45
104.36
109.98
109.59
110.28
110.27
108.65
108.65
133.8
0.0
r(C=O)
r(C-Br)
r(C1-C2)c
r(C2-C3)
r(C2-C4)
r(C2-H)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-Br)
∠(O=C-Br)
∠(C1-C2-C3)
∠(C1-C2-C4)
∠(C3-C2-C4)
∠(C1-C2-H)
∠(C3,4-C2-H)av
∠(C2-C3,4-H)av(CH3)
∠(H-C-H)av(CH3)
∠(H-C2-C1=O)
rms deviationd
(bond length)
(bond
angle)
MM3
gauche
1.1836
1.9840
1.5227
1.5422
1.5291
1.1152
1.1110
127.052
112.445
120.486
111.548
110.903
109.447
108.267
108.287
111.714
107.138
127.7
syn
1.1838
1.9843
1.5228
1.5400
1.5400
1.1131
1.1107
125.460
113.856
120.684
112.199
112.199
110.808
106.627
107.337
111.719
107.131
0.0
MM3 - Calculatedk
gauche
syn
-0.001
-0.001
0.001
-0.002
-0.005
-0.007
---------0.61
-1.84
0.29
0.45
0.31
1.34
2.55
1.44
1.62
1.44
-1.61
-0.73
0.82
2.27
-1.69
-2.25
1.43
1.45
-1.51
-1.52
-6.2
0.0
0.003
1.43
0.004
1.30
a)Converted from the r0 structure: (r(C=O) = 1.180, r(C-F) = 1.338, r(C1-C2) = 1.503, r(C2-C3) = 1.537,
r(C2-C4) = 1.527, r(C2-H) = 1.098, and r(C-H)av(CH3) = 1.094) from the microwave experiment
(reference 40). The scaling is approximated by comparing the rg structure from the electron diffraction
experiment (reference 19) and rs structure from the microwave experiment (reference 17) of acetyl
fluoride: (rg(C=O) - r0(C=O) = ~0.004, rg(C-F) - r0(C-F) = ~0.014, rg(C-C) - r0(C-C) = ~0.002, and rg(CH) - r0(C-H) = ~0.010), assuming r0 is close to rs.
b)Converted from the re structure: (r(C=O) = 1.170, r(C-F) = 1.329 (gauche) or 1.330 (syn), r(C1-C2) =
1.507 (gauche) or 1.506 (syn), r(C2-C3) = 1.538 (gauche) or 1.535 (syn), r(C2-C4) = 1.527 (gauche) or
1.535 (syn), r(C2-H) = 1.087 (gauche) or 1.082 (syn), and r(C-H)av(CH3) = 1.084) from ab initio RHF/631G* level calculation (present work and reference 40). For the scaling, see Table S2 (a).
c)Numbering of carbons is (C4 or C3)-C2-C1=O. C2-C4 bond is eclipsed to carbonyl group.
d)For the rms deviation of bond length, the C-H bond is excluded. For the rms deviation of bond angle,
any angle containing hydrogen is excluded.
e)Taken from reference 41 a). The ratio of gauche:syn is 88:12 at 298 °K.
f) Converted from the re structure: (r(C=O) = 1.168, r(C-Cl) = 1.792, r(C1-C2) = 1.517 (gauche) or 1.518
(syn), r(C2-C3) = 1.537 (gauche) or 1.533 (syn), r(C2-C4) = 1.527 (gauche) or 1.533 (syn), r(C2-H) =
1.084, and r(C-H)av(CH3) = 1.084) from ab initio RHF/6-31G* level calculation (Gaussian 90 program, in
this work). For the scaling, see Table S2 (b).
g)Boltzmann distribution averaged. The ratio of gauche:syn is 97:3 at 298 °K.
h)For the gauche conformer.
i)For the syn conformer.
j)This value of ∠(C3-C2-C4) appeared to be poorly determined, so this angle was not used in calculating
the rms deviation for the bond angle.
k)Converted from the re structures of gauche: (r(C=O) = 1.1865, r(C-Br) = 1.9593, r(C1-C2) = 1.5134,
r(C2-C3) = 1.5463, r(C2-C4) = 1.5359, and r(C2-H) = 1.0817, and r(C-H)av(CH3)= 1.0827) and syn:
(r(C=O) = 1.1869, r(C-Br) = 1.9622, r(C1-C2) = 1.5146, r(C2-C3,4) = 1.5405, and r(C2-H) = 1.0829, and
r(C-H)av(CH3) = 1.0835) conformers from ab initio RHF/3-21G* method (Gaussian 94 program, in this
work). For the scaling, see Table 3 (c).
Table S4. Structural parameters (bond lengths in Å, and bond angles in degrees) of
2,2-dimethylpropionyl fluoride, 2,2-dimethylpropionyl chloride, and 2,2dimethylpropionyl bromide
(a) 2,2-dimethylpropionyl fluoride
(CH3)3CCOF
r(C=O)
r(C-F)
r(C1-C2)b
r(C2-C3)
r(C2-C4,5)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-F)
∠(O=C-F)
∠(C-C-C(=O))av
∠(C-C-C)av(CH3)
∠(C-C-H)av(CH3)
∠(H-C-H)av(CH3)
∠(C3-C2-C1=O)
rms deviationc
Calculated,rga
1.187
1.366
1.524
--1.103
128.77
111.60
119.63
108.60
110.33
110.75
108.16
0.0
MM3
1.1850
1.3696
1.5191
1.5272
1.5385
1.1108
128.918
110.624
120.459
110.194
108.739
111.786
107.060
0.0
(bond length)
(bond angle)
MM3 - Calculateda
-0.002
0.004
-0.005
--0.008
0.15
-0.98
0.83
1.60
-1.59
1.04
-1.10
0.0
0.004
1.16
(b) 2,2-dimethylpropionyl chloride
(CH3)3CCOCl
r(C=O)
r(C-Cl)
r(C1-C2)b
r(C2-C3)
r(C2-C4,5)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-Cl)
∠(O=C-Cl)
∠(C-C-C(=O))av
∠(C-C-C)av (CH3)
∠(C-C-H)av(CH3)
∠(H-C-H)av(CH3)
∠(C3-C2-C1=O)
rms deviationc
Calculated,rgd
1.188
1.810
1.535
--1.094
127.13
115.13
118.14
108.84
110.09
110.75
108.16
0.0
(bond length)
(bond angle)
MM3
1.1865
1.8095
1.5291
1.5355
1.5453
1.1106
126.374
113.296
120.330
110.543
108.369
111.833
107.099
0.0
MM3 - Calculatedd
-0.001
0.000
-0.005
--0.016
-0.76
-1.83
2.19
1.70
-1.72
1.08
-1.06
0.0
0.003
1.71
(c) 2,2-dimethylpropionyl bromide
(CH3)3CCOBr
r(C=O)
r(C-Br)
r(C1-C2)b
r(C2-C3)
r(C2-C4,5)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-Br)
∠(O=C-Br)
∠(C-C-C(=O)) av
∠(C-C-C)av(CH3)
∠(C-C-H)av(CH3)
∠(H-C-H)av(CH3)
∠(C3-C2-C1=O)
rms deviationc
Calculated,rge
1.185
1.988
1.538
---127.08
114.17
118.75
108.67
110.25
110.30
108.63
0.0
(bond length)
(bond angle)
MM3
1.1839
1.9877
1.5305
1.5350
1.5450
1.1105
126.157
113.949
119.894
110.643
108.263
111.861
106.979
0.0
MM3 - Calculated,e
-0.001
0.000
-0.008
----0.92
-0.22
1.14
1.97
-1.99
1.56
-1.65
0.0
0.005
1.42
a)Converted from the re structure: (r(C=O) = 1.1699, r(C-F) = 1.3301, r(C1-C2) = 1.5150, r(C2-C3) =
1.5312, r(C2-C4,5) = 1.5398, and r(C-H)av = 1.0842) from ab initio RHF/6-31G* method (Gaussian 94
program, in this work). For the scaling, see Table S2 (a).
b)Numbering of carbons is (C3, C4, or C5)-C2-C1=O. C2-C3 bond is eclipsed to carbonyl group.
c)For the rms deviation of bond length, the C-H bond is excluded. For the rms deviation of bond angle,
any angle containing hydrogen is excluded.
d)Converted from the re structure: (r(C=O) = 1.1677, r(C-Cl) = 1.7965, r(C1-C2) = 1.5296, r(C2-C3) =
1.5349, r(C2-C4,5) = 1.5383, and r(C-H)av = 1.0838) from ab initio RHF/6-31G* method (Gaussian 94
program, in this work). For the scaling, see Table S2 (b).
e)Converted from the re structure: (r(C=O) = 1.1817, r(C-Br) = 1.9640, r(C1-C2) = 1.5227, r(C2-C3) =
1.5387, r(C2-C4) = 1.5414, and r(C-H)av(CH3)= 1.0827) from ab initio RHF/3-21G* method (Gaussian 94
program, in this work). For the scaling, see Table 3 (c).
Table S5. Characteristics of conformersa of n-butyryl fluoride, chloride, and bromide
found from MM3
syn-anti
syn-gauche
skew-anti
skew-gauche
0.0
180.0
2975
0
52.7
-5.1
-69.5
3824
849
24.6
-120.9
177.6
4197
1222
13.0
-122.5
60.4
4631
1656
6.2
0.0
180.0
2979
0
56.8
-5.4
-69.8
3829
850
26.4
-104.4
177.5
4320
1341
11.4
-108.4
59.3
4763
1784
5.3
0.0
180.0
3041
0
42.1
-4.8
-69.8
3885
844
19.8
-109.5
176.2
3746
705
25.1
-112.0
58.2
4130
1090
13.0
n-butyryl fluorideb
ω(C-C-C=O) (degree)
ω(C-C-C-C) (degree)
Esteric (cal/mol)
Erel (cal/mol)
conformer ratioc(%)
n-butyryl chloride
ω(C-C-C=O) (degree)
ω(C-C-C-C) (degree)
Esteric (cal/mol)
Erel (cal/mol)
conformer ratioc(%)
n-butyryl bromide
ω(C-C-C=O) (degree)
ω(C-C-C-C) (degree)
Esteric (cal/mol)
Erel (cal/mol)
conformer ratioc(%)
a)Definition of conformations of butyryl halides were adopted from the literature (reference 29).
b)In case of butyryl fluoride, two additional conformers, which are far less stable than syn-anti
conformer, were found; the one with ω(C-C-C=O) = 90.3 degrees, ω(C-C-C-C) = 64.4 degrees, and
Erel = 2355 cal/mol, and the other with ω(C-C-C=O) = 75.4 degrees, ω(C-C-C-C) = 63.3 degrees,
and Erel = 2389 cal/mol.
c)Calculated at 293 °K.
Table S6. Energy parameters and energy values (cal/mol) for 2-methylpropionyl
fluoride, 2-methylpropionyl chloride, and 2-methylpropionyl bromide;
Experiment, Ab initio, and MM3a
(a) 2-methylpropionyl fluoride
energy parameter
Ramanb,c
H ‡ (gauche --> syn)
H ‡ (gauche -->
gauche)
H 0 (syn - gauche)
1781
1289
E
G
0
0
Ab initiob
RHF/6-31G*
1784
1335
MM3
1878
1439
1320d
1240e
1198
(syn - gauche)
(syn - gauche)
1038
1156
1374
(b) 2-methylpropionyl chloride
energy parameter
H ‡ (gauche --> syn)
H ‡ (gauche -->
gauche)
H 0 (syn - gauche)
E 0 (syn - gauche)
G 0 (syn - gauche)
EDf
Ramanb,g
Ab initioa
RHF/6-31G*
3410
1010
MM3
3786
966
987(266)
1609
1693
1978
1100
700
(c) 2-methylpropionyl bromide
energy parameter
H ‡ (gauche --> syn)
H ‡ (gauche -->
gauche)
H 0 (syn - gauche)
E 0 (syn - gauche)
G 0 (syn - gauche)
Ab initioh
HF/3-21G*
4002
1904
1397
MM3
3976
1857
759
672
1138
a)The MM3 energy parameters were obtained in the same way for propionyl halides (see Table 6).
b)Taken from reference 40.
c)From the intensity ratio of temperature-dependent Raman line of s-trans and gauche forms in the
vapor phase.
d)From the gas phase Raman spectra.
e)From the liquid phase Raman spectra.
f)Taken from reference 41 a).
g)From the intensity ratio of temperature-dependent Raman line of s-trans and gauche forms in the liquid
phase.
h)Using the Gaussian 94 program, in this work.
The Dipole Moments of acyl halides. The dipole moments of acyl halides are
given in Table S1.
Table S1
Molecular Structures of the larger acyl halides. For n-butyryl halides, 2methylpropionyl bromide, and the 2,2-dimethylpropionyl halides, no experimentally
determined molecular structures have been reported. Therefore, theoretically calculated
structures (rg bond lengths were converted from the corresponding re bond lengths for all
ab initio calculations) were used for comparison purposes. For n-butyryl fluoride and 2,2dimethylpropionyl fluoride, the molecular structures from ab initio RHF/6-31G* level
calculations were scaled by comparing the rg structure19 and the re structure (ab initio
RHF/6-31G* method) of acetyl fluoride.
For n-butyryl chloride and 2,2-dimethyl-
propionyl chloride, the molecular structures from ab initio RHF/6-31G* level calculations
were scaled by comparing the rg structure21 and re structure (ab initio RHF/6-31G*
method) of acetyl chloride. For n-butyryl bromide, 2-methylpropionyl bromide, and 2,2dimethylpropionyl bromide, the molecular structures from ab initio RHF/3-21G* level
calculations were scaled by comparing the rg structure21 and re structure (ab initio RHF/321G* method) of acetyl bromide.
The molecular structures for the n-butyryl halides are represented in Table S2.
Table S2
The calculated molecular structures of n-butyryl fluoride, n-butyryl chloride, and n-butyryl
bromide, compared to the scaled structures, gave rms differences of 0.001 Å and 0.51
degrees, 0.002 Å and 0.72 degrees, and 0.004 Å and 0.72 degrees, respectively, for the
bond lengths (excluding C-H bonds) and bond angles (excluding angles containing
hydrogen).
For 2-methylpropionyl fluoride, the experimentally determined r0 molecular
structure of the gauche conformations available from a microwave experiment.i The re
structure of the syn form obtained from an RHF/6-31G* calculation was converted to rg
structure. Both the experimental and ab initio geometries were compared to the MM3
structure. The molecular geometries for the 2-methylpropionyl halides are represented in
Table S3. The rms differences for the bond lengths (excluding C-H bonds) and bond
angles (excluding any angle containing hydrogen) were 0.008 Å and 0.6 degrees, and
0.002 Å and 0.7 degrees for the syn and the gauche forms, respectively. The MM3
derived molecular structure of 2-methylpropionyl chloride was also compared to the rg
structure from electron diffraction.iia
The calculated structure for 2-methylpropionyl
chloride gave an rms difference of 0.006 Å for the bond lengths (excluding C-H bonds).
The value of the angle ∠(C3-C2-C4) from the experiment is too big, compared to either
our calculated value or to the ab initio value, and gave a 1.2 degrees rms deviation with
this angle excluded. The calculated molecular structures for the gauche and syn isomers
of 2-methylpropionyl bromide, compared to the molecular structures scaled as previously,
gave rms differences of 0.003 Å and 1.43 degrees, and 0.004 Å and 1.30 degrees,
respectively, for the bond lengths and bond angles.
Table S3
The molecular structures for the 2,2-dimethylpropionyl halides are shown in Table
S4. The calculated molecular structures of 2,2-dimethylpropionyl fluoride, chloride, and
Table S4
bromide, compared to the scaled structures, gave rms differences of 0.004 Å and 1.16
degrees, 0.003 Å and 1.68 degrees, and 0.005 Å and 1.42 degrees, respectively, for the
bond lengths (excluding C-H bonds) and bond angles (excluding any angle containing
hydrogen).
It was found that the C-X bond lengths in 2-methylpropionyl halides and 2,2dimethylpropionyl halides are increased, compared with the propionyl and n-butyryl
halides, which reflected the steric effects of the β-methyl groups.
Introducing an
additional methyl group in the β-position of propionyl fluoride gave no increase in the C-F
bond length from microwave studies,26a,40 but an approximately 0.003 Å increase in the CF bond length from our calculations and an approximately 0.001 Å increase according to
RHF/6-31G* calculations. The introduction of an additional methyl group in the βposition of propionyl chloride resulted in a 0.007 Å increase in the C-Cl bond length
according to electron diffraction studies,28,41a and approximately a 0.004 Å increase from
both ab initio quantum mechanics and molecular mechanics methods. Another methyl
group added to the β-position of propionyl bromide resulted in an approximately 0.004 Å
increase of the C-Br bond length with our calculations and a 0.003 Å increase from 321G* calculations.
Conformational analysis of the larger acyl halides. From the low resolution
microwave spectroscopy studies,iii it was reported that n-butyryl halides exist as syn-anti
(the first conformational symbol 'syn' for O=Cα-Cβ-Cγ torsional angle, and the second
symbol 'anti' for Cα-Cβ-Cγ-Cδ torsional angle) and syn-gauche conformers with roughly
the same energies. For n-butyryl fluoride, the less stable (about 0.3 kcal/mol) skew-anti
conformer was characterized. More precisely, our calculations on n-butyryl fluoride found
that the syn-gauche, skew-anti, skew-gauche, and gauche-gauche conformers have 849,
1222, and 1656 cal/mol, respectively, higher energies than the syn-anti conformer. The
corresponding energy values for n-butyryl chloride and bromide are 850, 1341, and 1784
cal/mol, and 844, 705, and 1090 cal/mol, respectively.
For the n-butyryl bromide,
interestingly the skew-anti form was more stable than the skew-gauche form.
Each
conformer of n-butyryl halides are compared in Table S5.
Table S5
From the torsional potential barriers of both acetyl fluoride and propionyl fluoride
from microwave studies, Stiefvater et al.27 in late 1960's predicted the conformations of 2methylpropionyl fluoride to be two equivalent optical isomers, gauche forms (one of
methyl group eclipsing the carbonyl group) and one syn conformer (the α-hydrogen
eclipsing the carbonyl group) with the gauche conformers being 1130 cal/mol (∆H0)
stable. Recently, Durig et al.40 determined an energy difference of 1320 cal/mol (∆H0)
from the temperature-dependent gas phase Raman spectrum. Our calculations showed
good agreement to the Stiefvater's predicted value27 and Durig's determined value40: the
gauche conformer was 1198 cal/mol (∆H0) or 1156 cal/mol (∆E0) more stable than the
syn. For 2-methylpropionyl chloride, our calculations showed that the gauche conformer
was 1609 cal/mol (∆H0) or 1693 cal/mol (∆E0) more stable than the syn. Our energy
difference was much higher than the value from a liquid Raman study41b (987 cal/mol,
∆H0), from electron diffraction study41a (700 cal/mol, ∆G0), or from ab initio MP2/631G* level calculation41a (910 cal/mol, ∆E0).
For 2-methylpropionyl bromide, our
molecular mechanics calculations showed that the gauche conformer was 672 cal/mol
(∆E0) or 759 cal/mol (∆H0) more stable than the syn conformer. The energy difference
between the stable conformers and other energy parameters for 2-methylpropionyl halides
are listed in Table S6.
Table S6
From the gas phase far-IR spectrum of 2,2-dimethylpropionyl fluoride and 2,2dimethylpropionyl chloride,34 the barriers to internal rotation have been determined to be
1755 cal/mol and 2307 cal/mol by applying the observed CC=O-C torsional fundamental
frequencies and Mathieu equation. From our calculations the barriers to internal rotation
are 1458 cal/mol and 2582 cal/mol for 2,2-dimethylpropionyl fluoride and chloride,
respectively.
Table S1. Dipole moments (in Debye) of acyl halides
(a) formyl fluoride
HCOF
exp.a
µtotal
2.02(4)
exp.b
Ab initioc
RHF/6-31G* MP2/6-31G*
1.99(3)
2.39
2.49
MM3
MM3 - exp.a
2.24
0.22
(b) formyl chloride
HCOCl
exp.d
µtotal
Ab initioc
RHF/6-31G* MP2/6-31G*
2.20
2.31
1.6(2)
MM3 - exp.d
MM3
2.25
0.65
(c) formyl bromide
HCOBr
µtotal
Ab initioe
RHF/3-21G*
2.17
MM3 - Ab initioe
MM3
2.23
0.06
(d) acetyl fluoride
CH3COF
exp.f
µtotal
Ab initioc
RHF/6-31G* MP2/6-31G*
3.09
3.26
2.96(3)
MM3
MM3 - exp.f
2.69
-0.27
(e) acetyl chloride
CH3COCl
exp.g
µtotal
2.713(8)
Ab initioc
RHF/6-31G* MP2/6-31G*
3.04
3.16
MM3
MM3 - exp.g
2.72
0.01
(f) acetyl bromide
CH3COBr
µtotal
Ab initioe
RHF/3-21G*
2.99
MM3
2.70
MM3-Ab initioe
-0.29
(g) propionyl fluoride
CH3CH2COF
exp.h
µtotal
s-trans
2.90(5)
gauche
3.08
Ab initioc
RHF/6-31G*
s-trans
gauche
3.10
3.25
MM3 - exp.h
MM3
s-trans
2.70
gauche
2.69
s-trans gauche
-0.20
-0.39
MM3
MM3 - exp.i
MM3 - Ab initioc
s-trans gauche
2.725
2.717
s-trans
0.10
(h) propionyl chloride
CH3CH2COCl
exp.i
µtotal
s-trans
2.63
Ab initioc
RHF/6-31G*
s-trans gauche
3.11
3.25
gauche
-0.53
(i) propionyl bromide
CH3CH2COBr
µtotal
Ab initioe
RHF/3-21G*
s-trans
gauche
3.02
3.18
MM3 - Ab initioe
MM3
s-trans
2.717
gauche
2.710
s-trans
-0.30
gauche
-0.47
(j) 2-methylpropionyl fluoride
(CH3)2CHCOF
exp.j
µtotal
gauche
2.98(1)
Ab initioc
RHF/6-31G*
gauche syn
3.18
3.32
MM3
gauche
2.699
syn
2.692
MM3 - exp.j
MM3 - Ab initioc
gauchec
-0.28
syn
-0.39
a)Taken from reference 17.
b)P. Favero and J. G. Baker, Nuovo Cimento, 17, 2942 (1960).
c)Using the Gaussian 90 program, in this work.
d)Taken from reference 18 a).
e)Using the Gaussian 94 program, in this work.
f)Taken from reference 20.
g)R. V. Galeev, L. N. Gunderova, A. H. Mamleev, and N. M. Pozdeev, Zh. Strukt. Khim., 36, 424 (1995).
h)Taken from reference 27.
i)G. T. Martin and J. R. Partington, J. Chem. Soc., 58, 158 (1936).
j)Taken from reference 40.
Table S2. Structural parameters (bond lengths in Å, and bond angles in degrees) of nbutyryl fluoride, n-butyryl chloride, and n-butyryl bromidea
(a) n-butyryl fluoride
CH3CH2CH2COF
r(C=O)
r(C-F)
r(C1-C2)c
r(C2-C3)
r(C3-C4)
r(C-H)av
∠(C-C=O)
∠(C-C-F)
∠(O=C-F)
∠(C1-C2-C3)
∠(C2-C3-C4)
∠(C-C-H)av
∠(H-C-H)av
∠(C-C-C=O)
rms deviationd
Calculated,rgb
1.186
1.363
1.510
--1.105
128.79
110.82
120.38
113.29
111.95
109.93
107.06
0.0
(bond length)
(bond angle)
MM3
1.1849
1.3640
1.5087
1.5207
1.5319
1.1121
129.315
110.101
120.584
112.743
112.381
109.910
107.163
0.0
MM3 - Calculatedb
-0.001
0.001
-0.001
--0.007
0.52
-0.72
0.20
-0.55
0.43
-0.02
0.10
0.0
0.001
0.51
MM3
1.1861
1.8017
1.5157
1.5276
1.5318
1.1124
127.484
111.702
120.814
112.713
112.344
109.906
107.187
0.0
MM3 - Calculatede
-0.001
0.000
0.003
--0.017
-0.07
-1.00
1.06
0.20
0.63
-0.15
0.03
0.0
0.002
0.72
(b)n-butyryl chloride
CH3CH2CH2COCl
r(C=O)
r(C-Cl)
r(C1-C2)c
r(C2-C3)
r(C3-C4)
r(C-H)av
∠(C-C=O)
∠(C-C-Cl)
∠(O=C-Cl)
∠(C1-C2-C3)
∠(C2-C3-C4)
∠(C-C-H)av
∠(H-C-H)av
∠(C-C-C=O)
rms deviationd
Calculated,rge
1.187
1.802
1.513
--1.095
127.55
112.70
119.75
112.51
111.71
110.05
107.15
0.0
(bond length)
(bond angle)
(c) n-butyryl bromide
CH3CH2CH2COBr
r(C=O)
r(C-Br)
r(C1-C2)c
r(C2-C3)
r(C3-C4)
r(C-H)av
∠(C-C=O)
∠(C-C-Br)
∠(O=C-Br)
∠(C1-C2-C3)
∠(C2-C3-C4)
∠(C-C-H)av
∠(H-C1-H)av
∠(C-C-C=O)
rms deviationd
Calculated,rgf
1.185
1.979
1.522
---127.67
111.56
120.77
111.65
111.09
109.87
107.77
0.0
(bond length)
(bond angle)
MM3
1.1833
1.9794
1.5161
1.5263
1.5318
1.1130
127.730
111.454
120.816
112.648
112.346
109.913
107.197
0.0
MM3 - Calculatedf
-0.002
0.000
-0.006
---0.06
-0.11
0.05
1.00
1.26
0.11
-0.57
0.0
0.004
0.72
a)Only the most stable syn-anti conformer is considered.
b)Converted from the re structure: (r(C=O) = 1.1691, r(C-F) = 1.3273, r(C1-C2) = 1.5005, r(C2-C3) =
1.5260, r(C3-C4) = 1.5275, and r(C-H)av = 1.0857) from ab initio RHF/6-31G* method (Gaussian 90
program, in this work). The scaling is done by comparing the rg structure from the electron diffraction
experiment (reference 19) and the re structure from ab initio RHF/6-31G* method of acetyl fluoride:
(rg(C=O) - re(C=O) = 0.017, rg(C-F) - re(C-F) = 0.036, rg(C-C(O)) - re(C-C(O)) = 0.009, and rg(C-H)av re(C-H)av = 0.019).
c)Numbering of carbons is C4-C3-C2-C1=O.
d)For the rms deviation of bond length, the C-H bond is excluded. For the rms deviation of bond angle,
any angle containing hydrogen is excluded.
e)Converted from the re structure: (r(C=O) = 1.1674, r(C-Cl) = 1.7889, r(C1-C2) = 1.5080, r(C2-C3) =
1.5275, r(C3-C4) = 1.5279, and r(C-H)av = 1.0854) from ab initio RHF/6-31G* method (Gaussian 90
program, in this work). The scaling is done by comparing the rg structure from the electron diffraction
experiment (reference 21) and the re structure from ab initio RHF/6-31G* method of acetyl chloride:
(rg(C=O) - re(C=O) = 0.020, rg(C-Cl) - re(C-Cl) = 0.013, rg(C-C(O)) - re(C-C(O)) = 0.005, and rg(C-H)av re(C-H)av = 0.010).
f)Converted from the re structure: (r(C=O) = 1.1866, r(C-Br) = 1.9551, r(C1-C2) = 1.5068, r(C2-C3) =
1.5360, r(C3-C4) = 1.5395, and r(C-H)av = 1.0839) from ab initio RHF/3-21G* method (Gaussian 94
program, in this work). For the scaling, see Table 3 (c).
Table S3. Structural parameters (bond lengths in Å, and bond angles in degrees) of 2methylpropionyl fluoride, 2-methylpropionyl chloride, and 2-methylpropionyl
bromide
(a) 2-methylpropionyl fluoride
(CH3)2CHCOF
Exp.,rga Calculated,rgb
gauche gauche syn
r(C=O)
1.184 1.187 1.187
r(C-F)
1.352 1.365 1.366
r(C1-C2)c
1.505 1.516 1.515
r(C2-C3)
1.539 --r(C2-C4)
1.529 --r(C2-H)
1.108 1.106 1.101
r(C-H)av(CH3)
1.104 1.103 1.103
128.7 128.82 128.37
∠(C-C=O)
111.3 111.14 111.64
∠(C-C-F)
120.0 120.04 119.99
∠(O=C-F)
110.4 109.84 110.20
∠(C1-C2-C3)
110.7 110.83 110.20
∠(C1-C2-C4)
110.0 112.45 110.95
∠(C3-C2-C4)
105.5 105.73 105.54
∠(C1-C2-H)
-108.86 -∠(C3,4-C2-H)av
∠(C2-C3,4-H)av(CH3) 110.6 110.71 110.73
-108.20 -∠(H-C-H)av(CH3)
118.5 118.5
0.0
∠(H-C2-C1=O)
d
rms deviation
(bond length)
(bond angle)
MM3
MM3 - Exp.,rga MM3 - Calc,rgb
gauche
syn
gauche
syn
1.1850 1.1849
0.001
-0.002
1.3675 1.3672
0.013
0.001
1.5139 1.5128
0.009
-0.002
1.5340 1.5339
-0.005
-1.5225 1.5339
-0.006
-1.1128 1.1088
0.005
0.008
1.1111 1.1110
0.007
0.008
129.090 128.431
0.39
0.06
110.383 110.770
-0.92
-0.87
120.518 120.799
0.52
0.81
111.124 111.125
0.72
0.93
111.238 111.125
0.54
0.93
110.087 110.525
0.09
0.43
107.655 107.584
2.16
2.04
108.309 108.171
--111.680 111.646
1.08
0.92
107.176 107.210
--119.4
0.0
0.9
0.0
0.008
0.59
0.002
0.75
(b) 2-methylpropionyl chloride
(CH3)2CHCOCl
ED.,rge
r(C=O)
1.186(3)
r(C-Cl)
1.804(4)
r(C1-C2)c
1.511(2)
r(C2-C3)
1.540(2)
r(C2-C4)
1.534(2)
r(C2-H)
1.088(6)
r(C-H)av(CH3)
1.108(6)
127.3(7)
∠(C-C=O)
113.6(5)
∠(C-C-Cl)
119.1
∠(O=C-Cl)
109.9(8)
∠(C1-C2-C3)
109.7(8)
∠(C1-C2-C4)
113.8(27)j
∠(C3-C2-C4)
106.8
∠(C1-C2-H)
-∠(C3,4-C2-H)av
∠(C2-C3,4-H)av(CH3) 111.7(18)
-∠(H-C-H)av(CH3)
h
130.1(37)
∠(H-C2-C1=O)
i
0.0
∠(H-C2-C1=O)
rms deviationd
(bond length)
(bond angle)
Ab initiof
gauche
syn
1.188
1.188
1.805
1.805
1.522
1.523
----1.094
1.094
1.094
1.094
127.16
126.13
113.54
114.86
119.30
119.01
109.78
111.60
109.74
111.60
111.97
112.19
106.87
103.09
109.19
108.95
110.50
110.73
108.24
108.18
136.1
0.0
MM3g
1.1863
1.8060
1.5219
1.5435
1.5305
1.1117
1.1109
127.052
112.235
120.694
110.997
111.011
109.581
108.430
108.338
111.677
108.332
131.9
0.0
MM3 - ED.,rge
0.000
0.002
0.011
0.004
-0.004
0.024
0.003
-0.25
-1.37
1.59
1.10
1.31
-4.22
1.63
-0.02
-1.8
0.0
0.006
1.22
(c) 2-methylpropionyl bromide
(CH3)2CHCOBr
Calculated,rgk
gauche
syn
1.185
1.185
1.983
1.986
1.528
1.530
--------127.66
127.30
112.16
113.36
120.18
119.34
109.00
110.76
109.28
110.76
111.06
111.54
107.45
104.36
109.98
109.59
110.28
110.27
108.65
108.65
133.8
0.0
r(C=O)
r(C-Br)
r(C1-C2)c
r(C2-C3)
r(C2-C4)
r(C2-H)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-Br)
∠(O=C-Br)
∠(C1-C2-C3)
∠(C1-C2-C4)
∠(C3-C2-C4)
∠(C1-C2-H)
∠(C3,4-C2-H)av
∠(C2-C3,4-H)av(CH3)
∠(H-C-H)av(CH3)
∠(H-C2-C1=O)
rms deviationd
(bond length)
(bond
angle)
MM3
gauche
1.1836
1.9840
1.5227
1.5422
1.5291
1.1152
1.1110
127.052
112.445
120.486
111.548
110.903
109.447
108.267
108.287
111.714
107.138
127.7
syn
1.1838
1.9843
1.5228
1.5400
1.5400
1.1131
1.1107
125.460
113.856
120.684
112.199
112.199
110.808
106.627
107.337
111.719
107.131
0.0
MM3 - Calculatedk
gauche
syn
-0.001
-0.001
0.001
-0.002
-0.005
-0.007
---------0.61
-1.84
0.29
0.45
0.31
1.34
2.55
1.44
1.62
1.44
-1.61
-0.73
0.82
2.27
-1.69
-2.25
1.43
1.45
-1.51
-1.52
-6.2
0.0
0.003
1.43
0.004
1.30
a)Converted from the r0 structure: (r(C=O) = 1.180, r(C-F) = 1.338, r(C1-C2) = 1.503, r(C2-C3) = 1.537,
r(C2-C4) = 1.527, r(C2-H) = 1.098, and r(C-H)av(CH3) = 1.094) from the microwave experiment
(reference 40). The scaling is approximated by comparing the rg structure from the electron diffraction
experiment (reference 19) and rs structure from the microwave experiment (reference 17) of acetyl
fluoride: (rg(C=O) - r0(C=O) = ~0.004, rg(C-F) - r0(C-F) = ~0.014, rg(C-C) - r0(C-C) = ~0.002, and rg(CH) - r0(C-H) = ~0.010), assuming r0 is close to rs.
b)Converted from the re structure: (r(C=O) = 1.170, r(C-F) = 1.329 (gauche) or 1.330 (syn), r(C1-C2) =
1.507 (gauche) or 1.506 (syn), r(C2-C3) = 1.538 (gauche) or 1.535 (syn), r(C2-C4) = 1.527 (gauche) or
1.535 (syn), r(C2-H) = 1.087 (gauche) or 1.082 (syn), and r(C-H)av(CH3) = 1.084) from ab initio RHF/631G* level calculation (present work and reference 40). For the scaling, see Table S2 (a).
c)Numbering of carbons is (C4 or C3)-C2-C1=O. C2-C4 bond is eclipsed to carbonyl group.
d)For the rms deviation of bond length, the C-H bond is excluded. For the rms deviation of bond angle,
any angle containing hydrogen is excluded.
e)Taken from reference 41 a). The ratio of gauche:syn is 88:12 at 298 °K.
f) Converted from the re structure: (r(C=O) = 1.168, r(C-Cl) = 1.792, r(C1-C2) = 1.517 (gauche) or 1.518
(syn), r(C2-C3) = 1.537 (gauche) or 1.533 (syn), r(C2-C4) = 1.527 (gauche) or 1.533 (syn), r(C2-H) =
1.084, and r(C-H)av(CH3) = 1.084) from ab initio RHF/6-31G* level calculation (Gaussian 90 program, in
this work). For the scaling, see Table S2 (b).
g)Boltzmann distribution averaged. The ratio of gauche:syn is 97:3 at 298 °K.
h)For the gauche conformer.
i)For the syn conformer.
j)This value of ∠(C3-C2-C4) appeared to be poorly determined, so this angle was not used in calculating
the rms deviation for the bond angle.
k)Converted from the re structures of gauche: (r(C=O) = 1.1865, r(C-Br) = 1.9593, r(C1-C2) = 1.5134,
r(C2-C3) = 1.5463, r(C2-C4) = 1.5359, and r(C2-H) = 1.0817, and r(C-H)av(CH3)= 1.0827) and syn:
(r(C=O) = 1.1869, r(C-Br) = 1.9622, r(C1-C2) = 1.5146, r(C2-C3,4) = 1.5405, and r(C2-H) = 1.0829, and
r(C-H)av(CH3) = 1.0835) conformers from ab initio RHF/3-21G* method (Gaussian 94 program, in this
work). For the scaling, see Table 3 (c).
Table S4. Structural parameters (bond lengths in Å, and bond angles in degrees) of
2,2-dimethylpropionyl fluoride, 2,2-dimethylpropionyl chloride, and 2,2dimethylpropionyl bromide
(a) 2,2-dimethylpropionyl fluoride
(CH3)3CCOF
r(C=O)
r(C-F)
r(C1-C2)b
r(C2-C3)
r(C2-C4,5)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-F)
∠(O=C-F)
∠(C-C-C(=O))av
∠(C-C-C)av(CH3)
∠(C-C-H)av(CH3)
∠(H-C-H)av(CH3)
∠(C3-C2-C1=O)
rms deviationc
Calculated,rga
1.187
1.366
1.524
--1.103
128.77
111.60
119.63
108.60
110.33
110.75
108.16
0.0
MM3
1.1850
1.3696
1.5191
1.5272
1.5385
1.1108
128.918
110.624
120.459
110.194
108.739
111.786
107.060
0.0
(bond length)
(bond angle)
MM3 - Calculateda
-0.002
0.004
-0.005
--0.008
0.15
-0.98
0.83
1.60
-1.59
1.04
-1.10
0.0
0.004
1.16
(b) 2,2-dimethylpropionyl chloride
(CH3)3CCOCl
r(C=O)
r(C-Cl)
r(C1-C2)b
r(C2-C3)
r(C2-C4,5)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-Cl)
∠(O=C-Cl)
∠(C-C-C(=O))av
∠(C-C-C)av (CH3)
∠(C-C-H)av(CH3)
∠(H-C-H)av(CH3)
∠(C3-C2-C1=O)
rms deviationc
Calculated,rgd
1.188
1.810
1.535
--1.094
127.13
115.13
118.14
108.84
110.09
110.75
108.16
0.0
(bond length)
(bond angle)
MM3
1.1865
1.8095
1.5291
1.5355
1.5453
1.1106
126.374
113.296
120.330
110.543
108.369
111.833
107.099
0.0
MM3 - Calculatedd
-0.001
0.000
-0.005
--0.016
-0.76
-1.83
2.19
1.70
-1.72
1.08
-1.06
0.0
0.003
1.71
(c) 2,2-dimethylpropionyl bromide
(CH3)3CCOBr
r(C=O)
r(C-Br)
r(C1-C2)b
r(C2-C3)
r(C2-C4,5)
r(C-H)av(CH3)
∠(C-C=O)
∠(C-C-Br)
∠(O=C-Br)
∠(C-C-C(=O)) av
∠(C-C-C)av(CH3)
∠(C-C-H)av(CH3)
∠(H-C-H)av(CH3)
∠(C3-C2-C1=O)
rms deviationc
Calculated,rge
1.185
1.988
1.538
---127.08
114.17
118.75
108.67
110.25
110.30
108.63
0.0
(bond length)
(bond angle)
MM3
1.1839
1.9877
1.5305
1.5350
1.5450
1.1105
126.157
113.949
119.894
110.643
108.263
111.861
106.979
0.0
MM3 - Calculated,e
-0.001
0.000
-0.008
----0.92
-0.22
1.14
1.97
-1.99
1.56
-1.65
0.0
0.005
1.42
a)Converted from the re structure: (r(C=O) = 1.1699, r(C-F) = 1.3301, r(C1-C2) = 1.5150, r(C2-C3) =
1.5312, r(C2-C4,5) = 1.5398, and r(C-H)av = 1.0842) from ab initio RHF/6-31G* method (Gaussian 94
program, in this work). For the scaling, see Table S2 (a).
b)Numbering of carbons is (C3, C4, or C5)-C2-C1=O. C2-C3 bond is eclipsed to carbonyl group.
c)For the rms deviation of bond length, the C-H bond is excluded. For the rms deviation of bond angle,
any angle containing hydrogen is excluded.
d)Converted from the re structure: (r(C=O) = 1.1677, r(C-Cl) = 1.7965, r(C1-C2) = 1.5296, r(C2-C3) =
1.5349, r(C2-C4,5) = 1.5383, and r(C-H)av = 1.0838) from ab initio RHF/6-31G* method (Gaussian 94
program, in this work). For the scaling, see Table S2 (b).
e)Converted from the re structure: (r(C=O) = 1.1817, r(C-Br) = 1.9640, r(C1-C2) = 1.5227, r(C2-C3) =
1.5387, r(C2-C4) = 1.5414, and r(C-H)av(CH3)= 1.0827) from ab initio RHF/3-21G* method (Gaussian 94
program, in this work). For the scaling, see Table 3 (c).
Table S5. Characteristics of conformersa of n-butyryl fluoride, chloride, and bromide
found from MM3
syn-anti
syn-gauche
skew-anti
skew-gauche
0.0
180.0
2975
0
52.7
-5.1
-69.5
3824
849
24.6
-120.9
177.6
4197
1222
13.0
-122.5
60.4
4631
1656
6.2
0.0
180.0
2979
0
56.8
-5.4
-69.8
3829
850
26.4
-104.4
177.5
4320
1341
11.4
-108.4
59.3
4763
1784
5.3
0.0
180.0
3041
0
42.1
-4.8
-69.8
3885
844
19.8
-109.5
176.2
3746
705
25.1
-112.0
58.2
4130
1090
13.0
n-butyryl fluorideb
ω(C-C-C=O) (degree)
ω(C-C-C-C) (degree)
Esteric (cal/mol)
Erel (cal/mol)
conformer ratioc(%)
n-butyryl chloride
ω(C-C-C=O) (degree)
ω(C-C-C-C) (degree)
Esteric (cal/mol)
Erel (cal/mol)
conformer ratioc(%)
n-butyryl bromide
ω(C-C-C=O) (degree)
ω(C-C-C-C) (degree)
Esteric (cal/mol)
Erel (cal/mol)
conformer ratioc(%)
a)Definition of conformations of butyryl halides were adopted from the literature (reference 29).
b)In case of butyryl fluoride, two additional conformers, which are far less stable than syn-anti
conformer, were found; the one with ω(C-C-C=O) = 90.3 degrees, ω(C-C-C-C) = 64.4 degrees, and
Erel = 2355 cal/mol, and the other with ω(C-C-C=O) = 75.4 degrees, ω(C-C-C-C) = 63.3 degrees,
and Erel = 2389 cal/mol.
c)Calculated at 293 °K.
Table S6. Energy parameters and energy values (cal/mol) for 2-methylpropionyl
fluoride, 2-methylpropionyl chloride, and 2-methylpropionyl bromide;
Experiment, Ab initio, and MM3a
(a) 2-methylpropionyl fluoride
energy parameter
Ramanb,c
H ‡ (gauche --> syn)
H ‡ (gauche -->
gauche)
H 0 (syn - gauche)
1781
1289
E
G
0
0
Ab initiob
RHF/6-31G*
1784
1335
MM3
1878
1439
1320d
1240e
1198
(syn - gauche)
(syn - gauche)
1038
1156
1374
(b) 2-methylpropionyl chloride
energy parameter
H ‡ (gauche --> syn)
H ‡ (gauche -->
gauche)
H 0 (syn - gauche)
E 0 (syn - gauche)
G 0 (syn - gauche)
EDf
Ramanb,g
Ab initioa
RHF/6-31G*
3410
1010
MM3
3786
966
987(266)
1609
1693
1978
1100
700
(c) 2-methylpropionyl bromide
energy parameter
H ‡ (gauche --> syn)
H ‡ (gauche -->
gauche)
H 0 (syn - gauche)
E 0 (syn - gauche)
G 0 (syn - gauche)
Ab initioh
HF/3-21G*
4002
1904
1397
MM3
3976
1857
759
672
1138
a)The MM3 energy parameters were obtained in the same way for propionyl halides (see Table 6).
b)Taken from reference 40.
c)From the intensity ratio of temperature-dependent Raman line of s-trans and gauche forms in the
vapor phase.
d)From the gas phase Raman spectra.
e)From the liquid phase Raman spectra.
f)Taken from reference 41 a).
g)From the intensity ratio of temperature-dependent Raman line of s-trans and gauche forms in the liquid
phase.
h)Using the Gaussian 94 program, in this work.