mm_mol_suppmat. 72KB Jun 05 2011 09:30:46 PM

(1)

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,

2-methylpropionyl bromide, and the 2,2-di2-methylpropionyl halides, no experimentally

determined molecular structures have been reported. Therefore, theoretically calculated

structures (r

g

bond lengths were converted from the corresponding r

e

bond lengths for all

ab initio

calculations) were used for comparison purposes. For

n-

butyryl fluoride and

2,2-dimethylpropionyl fluoride, the molecular structures from

ab initio

RHF/6-31G* level

calculations were scaled by comparing the r

g

structure

19

and the r

e

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 r

g

structure

21

and r

e

structure (

ab initio

RHF/6-31G*

method) of acetyl chloride. For

n-

butyryl bromide, 2-methylpropionyl bromide, and

2,2-dimethylpropionyl bromide, the molecular structures from

ab initio

RHF/3-21G* level

calculations were scaled by comparing the r

g

structure

21

and r

e

structure (

ab initio

RHF/3-21G* method) of acetyl bromide.

(2)

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 r

0

molecular

structure of the

gauche

conformations available from a microwave experiment.

i

The r

e

structure of the

syn

form obtained from an RHF/6-31G* calculation was converted to r

g

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 r

g

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

∠

(C

3

-C

2

-C

4

) 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

(3)

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

2,2-dimethylpropionyl 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

C-F 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

β

-position 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

(4)

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=C

_α

-C

_β

-C

_γ

torsional angle, and the second

symbol '

anti

' for C

_α

-C

_β

-C

_γ

-C

_δ

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

2-methylpropionyl 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 (

∆

H

0

)

stable. Recently, Durig

et al.

40

determined an energy difference of 1320 cal/mol (

∆

H

0

)

(5)

gauche

conformer was 1198 cal/mol (∆H

0

) or 1156 cal/mol (∆E

0

) more stable than the

syn.

For 2-methylpropionyl chloride, our calculations showed that the

gauche

conformer

was 1609 cal/mol (∆H

0

) or 1693 cal/mol (∆E

0

syn

. Our energy

difference was much higher than the value from a liquid Raman study

41b

(987 cal/mol,

∆H

0

), from electron diffraction study

41a

(700 cal/mol, ∆G

0

), or from

ab initio

MP2/6-31G* level calculation

41a

(910 cal/mol, ∆E

0

). For 2-methylpropionyl bromide, our

molecular mechanics calculations showed that the

gauche

conformer was 672 cal/mol

(∆E

0

) or 759 cal/mol (∆H

0

syn

conformer. The energy difference

between the stable conformers and other energy parameters for 2-methylpropionyl halides

are listed in Table S6.

Table S6

(6)

Table S1. Dipole moments (in Debye) of acyl halides

(a) formyl fluoride

HCOF

exp.a exp.b Ab initioc MM3 MM3 - exp.a RHF/6-31G* MP2/6-31G*

µtotal 2.02(4) 1.99(3) 2.39 2.49 2.24 0.22

(b) formyl chloride

HCOCl

exp.d Ab initioc MM3 MM3 - exp.d RHF/6-31G* MP2/6-31G*

µtotal 1.6(2) 2.20 2.31 2.25 0.65

(c) formyl bromide

HCOBr

Ab initioe MM3 MM3 - Ab initioe RHF/3-21G*

µtotal 2.17 2.23 0.06

(d) acetyl fluoride

CH

3

COF

exp.f Ab initioc_{MM3 MM3 - exp.}f

RHF/6-31G* MP2/6-31G*

µtotal 2.96(3) 3.09 3.26 2.69 -0.27

(e) acetyl chloride

CH

3

COCl

exp.g Ab initioc_{MM3 MM3 - exp.}g

RHF/6-31G* MP2/6-31G*

µtotal 2.713(8) 3.04 3.16 2.72 0.01

(f) acetyl bromide

CH

3

COBr

Ab initioe_{MM3 MM3-Ab initio}e

RHF/3-21G*

(7)

(g) propionyl fluoride

CH

3

CH

2

COF

exp.h Ab initioc

RHF/6-31G*

MM3 _{MM3 - exp.}h

s-trans gauche s-trans gauche s-trans gauche s-trans gauche µtotal 2.90(5) 3.08 3.10 3.25 2.70 2.69 -0.20 -0.39

(h) propionyl chloride

CH

3

CH

2

COCl

exp.i Ab initioc

RHF/6-31G*

MM3 _{MM3 - exp.}i_{MM3 - Ab initio}c

s-trans s-trans gauche s-trans gauche s-trans gauche µtotal 2.63 3.11 3.25 2.725 2.717 0.10 -0.53

(i) propionyl bromide

CH

3

CH

2

COBr

Ab initioe

RHF/3-21G*

MM3 _{MM3 - Ab initio}e

s-trans gauche s-trans gauche s-trans gauche

µtotal 3.02 3.18 2.717 2.710 -0.30 -0.47

(j) 2-methylpropionyl fluoride

(CH

3

)

2

CHCOF

exp.j Ab initioc

RHF/6-31G*

MM3 _{MM3 - exp.}j_{MM3 - Ab initio}c

gauche gauche syn gauche syn gauchec syn

µtotal 2.98(1) 3.18 3.32 2.699 2.692 -0.28 -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).

(8)

Table S2. Structural parameters (bond lengths in Å, and bond angles in degrees) of

n-butyryl fluoride,

n-

butyryl chloride, and

n-

butyryl bromide

a

(a)

n-

butyryl fluoride

CH

₃

CH

₂

CH

₂

COF

Calculated,rgb MM3 MM3 - Calculatedb

r(C=O) 1.186 1.1849 -0.001

r(C-F) 1.363 1.3640 0.001

r(C₁-C₂)c _1.510 _1.5087 _-0.001

r(C2-C3) -- 1.5207

--r(C3-C4) -- 1.5319

--r(C-H)_av 1.105 1.1121 0.007

∠(C-C=O) 128.79 129.315 0.52

∠(C-C-F) 110.82 110.101 -0.72

∠(O=C-F) 120.38 120.584 0.20

∠(C₁-C₂-C₃) 113.29 112.743 -0.55

∠(C2-C3-C4) 111.95 112.381 0.43

∠(C-C-H)_av 109.93 109.910 -0.02

∠(H-C-H)_av 107.06 107.163 0.10

∠(C-C-C=O) 0.0 0.0 0.0

rms deviationd _{(bond length)} _0.001

(bond angle) 0.51

(b)

n-

butyryl chloride

CH

₃

CH

₂

CH

₂

COCl

Calculated,r_ge _MM3 _{MM3 - Calculated}e

r(C=O) 1.187 1.1861 -0.001

r(C-Cl) 1.802 1.8017 0.000

r(C1-C2)c 1.513 1.5157 0.003

r(C2-C3) -- 1.5276

--r(C3-C4) -- 1.5318

--r(C-H)_av 1.095 1.1124 0.017

∠(C-C=O) 127.55 127.484 -0.07

∠(C-C-Cl) 112.70 111.702 -1.00

∠(O=C-Cl) 119.75 120.814 1.06

∠(C1-C2-C3) 112.51 112.713 0.20

∠(C2-C3-C4) 111.71 112.344 0.63

∠(C-C-H)_av 110.05 109.906 -0.15

∠(H-C-H)_av 107.15 107.187 0.03

∠(C-C-C=O) 0.0 0.0 0.0

[image:8.612.92.522.457.701.2]

(9)

(c)

n-

butyryl bromide

CH

₃

CH

₂

CH

₂

COBr

Calculated,rgf MM3 MM3 - Calculatedf

r(C=O) 1.185 1.1833 -0.002

r(C-Br) 1.979 1.9794 0.000

r(C1-C2)c 1.522 1.5161 -0.006

r(C2-C3) -- 1.5263

--r(C₃-C₄) -- 1.5318

--r(C-H)av -- 1.1130

--∠(C-C=O) 127.67 127.730 0.06

∠(C-C-Br) 111.56 111.454 -0.11

∠(O=C-Br) 120.77 120.816 0.05

∠(C₁-C2-C3) 111.65 112.648 1.00

∠(C₂-C3-C4) 111.09 112.346 1.26

∠(C-C-H)_av 109.87 109.913 0.11

∠(H-C1-H)av 107.77 107.197 -0.57

∠(C-C-C=O) 0.0 0.0 0.0

(bond angle) 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 r_g 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 r_e 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

-r_e(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

(10)

Table S3. Structural parameters (bond lengths in Å, and bond angles in degrees) of

2-methylpropionyl fluoride, 2-2-methylpropionyl chloride, and 2-2-methylpropionyl

bromide

(a) 2-methylpropionyl fluoride

(CH

₃

)

₂

CHCOF

Exp.,rga Calculated,rgb MM3 MM3 - Exp.,rga MM3 - Calc,rgb

gauche gauche syn gauche syn gauche syn

r(C=O) 1.184 1.187 1.187 1.1850 1.1849 0.001 -0.002

r(C-F) 1.352 1.365 1.366 1.3675 1.3672 0.013 0.001

r(C1-C2)c 1.505 1.516 1.515 1.5139 1.5128 0.009 -0.002

r(C2-C3) 1.539 -- -- 1.5340 1.5339 -0.005

--r(C2-C4) 1.529 -- -- 1.5225 1.5339 -0.006

--r(C2-H) 1.108 1.106 1.101 1.1128 1.1088 0.005 0.008

r(C-H)av(CH3) 1.104 1.103 1.103 1.1111 1.1110 0.007 0.008

∠(C-C=O) 128.7 128.82 128.37 129.090 128.431 0.39 0.06

∠(C-C-F) 111.3 111.14 111.64 110.383 110.770 -0.92 -0.87

∠(O=C-F) 120.0 120.04 119.99 120.518 120.799 0.52 0.81

∠(C₁-C₂-C₃) 110.4 109.84 110.20 111.124 111.125 0.72 0.93

∠(C1-C2-C4) 110.7 110.83 110.20 111.238 111.125 0.54 0.93

∠(C₃-C₂-C₄) 110.0 112.45 110.95 110.087 110.525 0.09 0.43

∠(C1-C2-H) 105.5 105.73 105.54 107.655 107.584 2.16 2.04

∠(C_3,4-C₂-H)_av -- 108.86 -- 108.309 108.171 --

--∠(C2-C3,4-H)av(CH3) 110.6 110.71 110.73 111.680 111.646 1.08 0.92

∠(H-C-H)av(CH3) -- 108.20 -- 107.176 107.210 --

--∠(H-C₂-C₁=O) 118.5 118.5 0.0 119.4 0.0 0.9 0.0

rms deviationd _{(bond length)} _0.008 _0.002

[image:10.612.91.521.210.523.2]

(11)

(b) 2-methylpropionyl chloride

(CH

₃

)

₂

CHCOCl

ED.,r_ge _{Ab initio}f _MM3g _{MM3 - ED.,r}

ge gauche syn

r(C=O) 1.186(3) 1.188 1.188 1.1863 0.000

r(C-Cl) 1.804(4) 1.805 1.805 1.8060 0.002

r(C1-C2)c 1.511(2) 1.522 1.523 1.5219 0.011

r(C2-C3) 1.540(2) -- -- 1.5435 0.004

r(C2-C4) 1.534(2) -- -- 1.5305 -0.004

r(C2-H) 1.088(6) 1.094 1.094 1.1117 0.024

r(C-H)_av(CH₃) 1.108(6) 1.094 1.094 1.1109 0.003

∠(C-C=O) 127.3(7) 127.16 126.13 127.052 -0.25

∠(C-C-Cl) 113.6(5) 113.54 114.86 112.235 -1.37

∠(O=C-Cl) 119.1 119.30 119.01 120.694 1.59

∠(C1-C2-C3) 109.9(8) 109.78 111.60 110.997 1.10

∠(C₁-C₂-C₄) 109.7(8) 109.74 111.60 111.011 1.31

∠(C3-C2-C4) 113.8(27)j 111.97 112.19 109.581 -4.22

∠(C1-C2-H) 106.8 106.87 103.09 108.430 1.63

∠(C3,4-C2-H)av -- 109.19 108.95 108.338

--∠(C2-C3,4-H)av(CH3) 111.7(18) 110.50 110.73 111.677 0.02

∠(H-C-H)av(CH3) -- 108.24 108.18 108.332

--∠(H-C₂-C₁=O)h _130.1(37) _136.1 _131.9 _1.8

∠(H-C₂-C₁=O)i _0.0 _0.0 _0.0 _0.0

(12)

(

c) 2-methylpropionyl bromide

(CH

₃

)

₂

CHCOBr

Calculated,rgk MM3 MM3 - Calculatedk

gauche syn gauche syn gauche syn

r(C=O) 1.185 1.185 1.1836 1.1838 -0.001 -0.001

r(C-Br) 1.983 1.986 1.9840 1.9843 0.001 -0.002

r(C1-C2)c 1.528 1.530 1.5227 1.5228 -0.005 -0.007

r(C2-C3) -- -- 1.5422 1.5400 --

--r(C2-C4) -- -- 1.5291 1.5400 --

--r(C2-H) -- -- 1.1152 1.1131 --

--r(C-H)av(CH3) -- -- 1.1110 1.1107 --

--∠(C-C=O) 127.66 127.30 127.052 125.460 -0.61 -1.84

∠(C-C-Br) 112.16 113.36 112.445 113.856 0.29 0.45

∠(O=C-Br) 120.18 119.34 120.486 120.684 0.31 1.34

∠(C₁-C₂-C₃) 109.00 110.76 111.548 112.199 2.55 1.44

∠(C1-C2-C4) 109.28 110.76 110.903 112.199 1.62 1.44

∠(C₃-C₂-C₄) 111.06 111.54 109.447 110.808 -1.61 -0.73

∠(C1-C2-H) 107.45 104.36 108.267 106.627 0.82 2.27

∠(C_3,4-C₂-H)_av 109.98 109.59 108.287 107.337 -1.69 -2.25

∠(C2-C3,4-H)av(CH3) 110.28 110.27 111.714 111.719 1.43 1.45

∠(H-C-H)av(CH3) 108.65 108.65 107.138 107.131 -1.51 -1.52

∠(H-C₂-C₁=O) 133.8 0.0 127.7 0.0 -6.2 0.0

rms deviationd _{(bond length)} _0.003 _0.004

(bond angle)

1.43 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 r_g 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

(C-H) - 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/6-31G* 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).

(13)

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

(14)

Table S4. Structural parameters (bond lengths in Å, and bond angles in degrees) of

dimethylpropionyl fluoride, dimethylpropionyl chloride, and

2,2-dimethylpropionyl bromide

(a) 2,2-dimethylpropionyl fluoride

(CH

₃

)

₃

CCOF

Calculated,rga MM3 MM3 - Calculateda

r(C=O) 1.187 1.1850 -0.002

r(C-F) 1.366 1.3696 0.004

r(C1-C2)b 1.524 1.5191 -0.005

r(C2-C3) -- 1.5272

--r(C2-C4,5) -- 1.5385

--r(C-H)av(CH3) 1.103 1.1108 0.008

∠(C-C=O) 128.77 128.918 0.15

∠(C-C-F) 111.60 110.624 -0.98

∠(O=C-F) 119.63 120.459 0.83

∠(C-C-C(=O))av 108.60 110.194 1.60

∠(C-C-C)av(CH3) 110.33 108.739 -1.59

∠(C-C-H)av(CH3) 110.75 111.786 1.04

∠(H-C-H)_av(CH₃) 108.16 107.060 -1.10

∠(C₃-C₂-C₁=O) 0.0 0.0 0.0

rms deviationc _{(bond length)} _0.004

(bond angle) 1.16

(b) 2,2-dimethylpropionyl chloride

(CH

₃

)

₃

CCOCl

Calculated,rgd MM3 MM3 - Calculatedd

r(C=O) 1.188 1.1865 -0.001

r(C-Cl) 1.810 1.8095 0.000

r(C1-C2)b 1.535 1.5291 -0.005

r(C₂-C₃) -- 1.5355

--r(C2-C4,5) -- 1.5453

--r(C-H)av(CH3) 1.094 1.1106 0.016

∠(C-C=O) 127.13 126.374 -0.76

∠(C-C-Cl) 115.13 113.296 -1.83

∠(O=C-Cl) 118.14 120.330 2.19

∠(C-C-C(=O))av 108.84 110.543 1.70

∠(C-C-C)av (CH3) 110.09 108.369 -1.72

∠(C-C-H)av(CH3) 110.75 111.833 1.08

∠(H-C-H)av(CH3) 108.16 107.099 -1.06

∠(C₃-C₂-C₁=O) 0.0 0.0 0.0

[image:14.612.94.523.471.713.2]

(15)

(c) 2,2-dimethylpropionyl bromide

(CH

₃

)

₃

CCOBr

Calculated,r_ge _MM3 _{MM3 - Calculated,}e

r(C=O) 1.185 1.1839 -0.001

r(C-Br) 1.988 1.9877 0.000

r(C1-C2)b 1.538 1.5305 -0.008

r(C2-C3) -- 1.5350

--r(C2-C4,5) -- 1.5450

--r(C-H)av(CH3) -- 1.1105

--∠(C-C=O) 127.08 126.157 -0.92

∠(C-C-Br) 114.17 113.949 -0.22

∠(O=C-Br) 118.75 119.894 1.14

∠(C-C-C(=O))_av 108.67 110.643 1.97

∠(C-C-C)av(CH3) 110.25 108.263 -1.99

∠(C-C-H)_av(CH₃) 110.30 111.861 1.56

∠(H-C-H)av(CH3) 108.63 106.979 -1.65

∠(C₃-C₂-C₁=O) 0.0 0.0 0.0

(bond angle) 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-C_4,5) = 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

(16)

Table S5. Characteristics of conformers

a

of

n-

butyryl fluoride, chloride, and bromide

found from MM3

syn-anti syn-gauche skew-anti skew-gauche

n-

butyryl fluoride

b

ω(C-C-C=O) (degree) 0.0 -5.1 -120.9 -122.5

ω(C-C-C-C) (degree) 180.0 -69.5 177.6 60.4

Esteric (cal/mol) 2975 3824 4197 4631

Erel (cal/mol) 0 849 1222 1656

conformer ratioc(%) 52.7 24.6 13.0 6.2

n-

butyryl chloride

ω(C-C-C=O) (degree) 0.0 -5.4 -104.4 -108.4

ω(C-C-C-C) (degree) 180.0 -69.8 177.5 59.3

Esteric (cal/mol) 2979 3829 4320 4763

Erel (cal/mol) 0 850 1341 1784

n-

butyryl bromide

ω(C-C-C=O) (degree) 0.0 -4.8 -109.5 -112.0

ω(C-C-C-C) (degree) 180.0 -69.8 176.2 58.2

E_steric_(cal/mol) 3041 3885 3746 4130

Erel (cal/mol) 0 844 705 1090

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.

[image:16.612.96.523.159.445.2]

(17)

Table S6. Energy parameters and energy values (cal/mol) for 2-methylpropionyl

fluoride, 2-methylpropionyl chloride, and 2-methylpropionyl bromide;

Experiment, Ab initio, and MM3

a

(a) 2-methylpropionyl fluoride

energy parameter Ramanb,c _{Ab initio}b

RHF/6-31G*

MM3

H ‡ ₍_gauche_-->_syn₎ ₁₇₈₁ ₁₇₈₄ ₁₈₇₈

H ‡ ₍_gauche_--> gauche)

1289 1335 1439

H 0₍_syn_-_gauche₎ ₁₃₂₀d

1240e 1198

E 0₍_syn_-_gauche₎ ₁₀₃₈ ₁₁₅₆

G 0₍_syn_-_gauche₎ ₁₃₇₄

(b) 2-methylpropionyl chloride

energy parameter EDf _Ramanb,g _{Ab initio}a

RHF/6-31G*

MM3

H ‡ ₍_gauche_-->_syn₎ ₃₄₁₀ ₃₇₈₆

1010 966

H 0₍_syn_-_gauche₎ _987(266) ₁₆₀₉

E 0₍_syn_-_gauche₎ ₁₁₀₀ ₁₆₉₃

G 0₍_syn_-_gauche₎ ₇₀₀ ₁₉₇₈

(c) 2-methylpropionyl bromide

energy parameter Ab initioh

HF/3-21G*

MM3

H ‡ ₍_gauche_-->_syn₎ ₄₀₀₂ ₃₉₇₆

1904 1857

H 0₍_syn_-_gauche₎ ₇₅₉

E 0₍_syn_-_gauche₎ ₁₃₉₇ ₆₇₂

G 0₍_syn_-_gauche₎ 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.

[image:17.612.92.521.481.580.2]

(18)

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.