bent and twisted amides - david a....
TRANSCRIPT
![Page 1: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/1.jpg)
Synthesis, Spectroscopy, Reactivity, Utility
Bent and Twisted Amides
Reviews:
Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil
Structure and Reactivity J.F. Liebman, A. Greenberg eds. CH 4 Twisted Bridgehead Bicyclic Lactams, A. Greenberg
J.K. Lynch Group Meeting 4/30/91
01-TitlePage 5/1/91 3:03 PM
![Page 2: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/2.jpg)
X X
Justus Lieb.Ann.Chem. 437,1(1924) J.Bredt, H.Thouet, J.SchmitzACIEE 12, 464 (1973) G. Koebrich (review)
Bredt's Rule
(2)(1)
" in systems of the camphane and pinaneseries and related compounds (1) and (2),the branching points A and B of the carbon bridges (bridgeheads) cannot be involved ina carbon double bond."
B
A
B
A
-HBr -H2O
-H2O
-HBr
O
O
O O
O
OCOOH
COOH
Br
COOR
Br
COOR
COOR COOR
COOH
COOHO
O
O
02-Bredt'sRule-1 5/1/91 11:46 AM
![Page 3: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/3.jpg)
Chem. Rev. 83, 549 (1983) H.K. Hall Jr., S. El-Skekeil
[3.2.1][3.2.1][2.2.2][2.2.1]
Detected by Trapping
Isolated Bridgehead Olefins
Bredt's Rule- Strained Bridgehead Olefins
[4.2.1][4.2.1][3.3.1]
03-Bredt'sRule-2 4/28/91 1:49 PM
![Page 4: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/4.jpg)
Tet. 21, 2257, (1965) V.H. Pracejus, M. Kehlen, H. Kehlen, H. Matschiner
.HCl .HCl
SOCl2
60°C, 4h
IgnitedK2CO3
CHCl3
aq. K2CO3
C7H11ONCal N 11.20Found N 11.61
.HCl
Et3N
R1=R2=R3=HR1=R2=H, R3=CH3 Note: pka=5.33R1=H, R2=R3=CH3R1=R3=CH3, R2=HR1=R2=R3=CH3
J.Gen.Chem.USSR (Eng.Trans) 27, 83 (1957) L.N. Yakhontov, M.V. Rubsitov
Structure and Reactivity CH4, p140 A.Greenberg
Synthesis of Bridgehead Bicyclic Lactams
N
ONH
COOH COCl
NH
O
N
R3R3
R1
R2NH
COCl
04-Syn-His 5/1/91 11:56 AM
![Page 5: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/5.jpg)
Et3N
ClCOOEt
2) NaOH 3) NaBH4
1) CH2=CHCOOEt
JOC 34, 183 (1969) M. Denzer, H. Ott
>90%
DCC, CH3CN
Synthesis-Active Ester
JOC 51, 2676 (1986) R. S. Brown, V. Somayaji
DCC, CH3CN
2) HCl 3) KOH
1) Ag2O, EtOH
N
O
CHN2
TOS
N
TOS
COOH
N O
X X
XX
N
H
OH
O
X
NO
NH
N
Cl
Ph Ph
Cl
HN
N
COOH N
NCl
Ph
O
05-Syn1-ActiveEster 4/27/91 9:22 AM
![Page 6: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/6.jpg)
(5,6,7 membered lactams)
1.0 Bu2SnO
Toluene∆, 12hrs
77%
(∆, 2.5%)
Synthesis- DibutylTinOxide
JACS 105, 7130(1983) K. Steliou, M. PoupartHelv. 70, 1981(1987) R. Brehm, D. Ohnhauser, H.Gerlach
(CH2)n
NH2
(CH2)n
n=3,4,5
(CH2)n
+ Bu2SnO
Bu2SnO
-H2O
(CH2)n(CH2)n polyamide
NH
OHON
O
H2N (CH2)nCOOH
O
OSnR2
OH
O
SnR2
NH
O O
NH
Sn
R
R
OO
O
O
NH2
H2N
06-Syn2TinOxide 4/30/91 5:35 PM
![Page 7: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/7.jpg)
Synthesis- Pd, Rh
JACS 108, 6431 (1986) R.M. Williams, B.H. Lee
C6H6, ∆, 1hr
Rh2(OAc)4
CH3CN
TsN3, 25°C 50%
JCS Chem Comm. 1696(1986) R. Grigg, et. al
R=H 88%R=Ph 55%
CH3CN, 30-80 °CEt4NCl, K2CO3
0.1 Pd(OAc)2, 0.2 PP3IN
O
R
N
R
O
N
O
Me
tBuO2C
H
O
H
OtBu
O O
Me
O
NHNH
O
Me
OO
OtBuCN2
07-Syn3Rh,Pd 4/27/91 10:50 AM
![Page 8: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/8.jpg)
spiro pyrazolium ylide
+
40-50% overall
-EtOH, ∆
isolable60-70%
∆
[1,4]
>95%
1,4 elim.EtOH
X=CH2CH2
CH2OCH2
(CH2)3 (CH2)4
Synthesis- Spiro Pyrazolium Ylides
6Πelectrocy.
JOC 50, 909 (1985) J. Chuche et. al.
X N NH2
EtO CO2Et
CO2EtCO2Et
CO2EtHNNX
NXHN CO2Et
CO2Et
N+-N
X
CO2Et
O
CO2Et
NX
N O
N CO2Et
C
O
N
X
08-Syn4SriroYlides 4/30/91 9:19 AM
![Page 9: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/9.jpg)
1695 cm-1
1716 cm-1
1641 cm-1
1750 cm-1
1791 cm-1
1745-60 cm-1
1795 cm-1
1730 cm-1
1750 cm-1
1755 cm-1
1705 cm-1
Spectroscopy-IR
O
N O
O
CH3
N
CH3
O
O O
N
RN
O
Me
tBuO2C
H
O
H
N NO
O
NH
09-IR 5/1/91 11:49 AM
![Page 10: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/10.jpg)
JCS Chem Comm 814 (1981) G.L. Buchanon
185.7 ppm169 ppm 210 ppm
188 ppm192 ppm213 ppm
Spectroscopy- NMR
9 8
6
41H
13C
W coupling Heq-Heq C's 6,8,9
none to C-4
N OO
CH3
N
CH3
O
N NOO
O
ON
Ph
N
O
Hax
Heq
Hax
Heq
Heq
10-NMR 4/30/91 9:26 AM
![Page 11: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/11.jpg)
Haemanthidine
MnO2
CHCl3
NaBH4
MeOH
"facile"
aq. AcOH 100%
NaBH4Pt, AcOH
JOC 34, 183 (1969) M. Denzer, H. Ott
JACS 80, 2590 (1958) S.Uyeo, H.M. Fales, R.J. Highet, W.C. Wildman
Reactivity-Reduction
N
O
O
OH
OCH3
OHOCH3
O
NO
O
OH
N
N
Ph
O
Cl
ClN
HO
Ph
NH
NH
NH
Cl
O
Ph
Ph
O
Cl
NH
N
Me
11-React.-NaBH4 4/30/91 5:48 PM
![Page 12: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/12.jpg)
HClCH3I
2) H2O
1) PhLi
R= OH, MeO, HNNH2
NHOH, morpholineRH
3) Quaternization reactions that leave the bicyclic ring intact occur with HCl and CH3I
2) Nucleophilic reagents, aprotic media break the N-C(CH3)2 bond
1) Protic nucleophilic reagents break the lactam linkage
Reactivity-General
Cl-I-
N OMe
Me
N+Me
MeO
COOR
Me
Me
Me
Me NH
NMe
MeO
N OMe
Me
NH
OMe
Me
Me
Me
CN
Me
Me
OH
Me
MeON
H
N+ OMe
Me
Me H
CNHO
12-React-Gen 4/29/91 6:33 PM
![Page 13: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/13.jpg)
Twist and Tilt Deformations
Twist Angle Φ
Tilt Angle Θ
JOC 51, 2676 (1986) V. Somayaji, R.S. Brown
Θ
Φ
NY
Z
X
Y
X
Z
N
C3O
C4C1
N
N
C4C3
O C1
C4
O
C3C1
C1
O C3
C4
13-Twist/Tilt 4/30/91 9:30 AM
![Page 14: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/14.jpg)
Reactivity-Twist vs Tilt
kOH M-1s-1kOH M
-1s-1
JOC 52, 805 (1987) H.S. Tilk, R.S. Brown
6.0 X 10-6kOH M-1s-1
0.271.12.816.9
kOH M-1s-1X
OCH3HBrNO2
Twist Angle Φ 0+- 10°Tilt Angle Θ 34°
JOC 15, 2676 (1986) V. Somayaji, R.S. Brown
7.55 X 10-66.0 X 102.62 X 102
kOH M-1s-1
X-rayTwist Angle Φ= 30-35°Tilt Angle Θ= 15-20°
MModTwist Angle Φ ~ 90°Tilt Angle Θ∼15-20°
N O
N
NO
NH
O
O
X
N
Me
Me
O
14-HydrolBBL 4/30/91 5:51 PM
![Page 15: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/15.jpg)
JOC 51, 4866 (1986) V. Somayaji, K.I. Skorey, R.S. Brown, R.G. BallJOC 51, 4866 (1986) V. Somayaji, K.I. Skorey, R.S. Brown, R.G. Ball
15-JKLSer1 4/30/91 2:27 PM
![Page 16: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/16.jpg)
JOC 51, 4866 (1986) V. Somayaji K.I. Skorey, R.S. Brown, R.G. Ball
Acylation of β-Amino Alcohols Model for Serine Protease
++
R=H, R'= CH2OHR=H, R'= CH3R=CH3, R'=CH2OHR= R'=CH3
R=CH3+ I-
R= :
N
O
(CH3)2NOH
R
N
N R'
R
16-JKLSer2 4/30/91 3:16 PM
![Page 17: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/17.jpg)
R=CH3+ I-
R= :R=H, R'= CH2OHR=H, R'= CH3R=CH3, R'=CH2OHR= R'=CH3
+ +
Acylation of β-Amino Alcohols
JOC 51, 4866 (1986) V. Somayaji K.I. Skorey, R.S. Brown, R.G. Ball
H3C O
ONO2
(CH3)2NOH
R
N
N R'
R
17-JKLSer3 4/30/91 3:13 PM
![Page 18: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/18.jpg)
Science 863 (1990) M.K. Rosen, R.F Standert, A. Galat, M. Nakatsuka, S.L. Schreiber Science 863 (1990) M.K. Rosen, R.F Standert, A. Galat, M. Nakatsuka, S.L. Schreiber
Mechanism of Rotomase Enzymes
18-JKLFK1 4/30/91 1:49 PM
![Page 19: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/19.jpg)
Biochemistry 3813 (1990) R.K. Harrison, R.L. SteinJOC 4984 (1990) M.W. Albers, C.T. Walsh, S.L. SchreiberBiochemistry 3813 (1990) R.K. Harrison, R.L. SteinJOC 4984 (1990) M.W. Albers, C.T. Walsh, S.L. Schreiber
Rotomase Inhibitors- Leucine Twisted Amide Mimics
19-JKLFK2 4/30/91 2:03 PM
![Page 20: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/20.jpg)
Science 251, 283 (1991) S. L. SchreiberScience 251, 283 (1991) S. L. Schreiber
Rotomase Inhibitors
20-JKLFK3 4/30/91 2:13 PM
![Page 21: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/21.jpg)
Rotational Barriers, Amide and Ester Resonance
∆G-exp
∆G-exp
∆G-exp
∆G-exp
∆G-calc
∆G-calc
∆G-calc
∆G-calc
3.900 Kcal/mole
4.61 Kcal/mole
4.750 Kcal/mole
5.59 Kcal/mole
3.850 Kcal/mole
1.19 Kcal/mole
1.15 Kcal/mole
8.51 Kcal/mole
8.63 Kcal/mole
K.B. Wiberg, K.E. Laidig JACS 109, 5935 (1987)
OH
O
H
O
O
H
H
O
OCH3
H
O
CH3
O
H
OCH3
O
H3C H3C
O
O
CH3
H
O
O
H H
H
H
HHO
O
H
21-Wiberg1 4/30/91 10:38 AM
![Page 22: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/22.jpg)
K.B. Wiberg, K.E. Laidig JACS 109, 5935 (1987)
2.3 Kcal/mole∆G-calc
Rotational Barrier
Exp 18-19 Kcal/moleCalc 15.3 Kcal/mole
"calculated satisfactorally"
Calc. RC-O Å
1.233
1.400
1.188
1.193
model for 50%charge transfer
C-O single bond
no resonance
indicative of a normal C=Odouble bond, little evidenceof loss of double bond character
Amide Resonance?
H
O
N NH
H
H H
H NH
H
O
H
O
H3C O-
O
H3CO
CH3
H3CH
O
H N
O
H
H
O
N
H
HH
H N+H
H
O-
22-Wiberg2 4/30/91 11:09 AM
![Page 23: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/23.jpg)
DE Kcal/mole (calc)
µ(D)
rC=OrC-NrC-HrN-H
4.095(3.85exp)
0.0
1.19271.34891.09100.99570.9923
15.34
1.573
1.18321.42731.08761.0055
17.60
4.080
1.17891.42301.09431.0046
Calculated energies,dipolemoment and bond lenghts
C-N bond length decreases 0.08Å suggests some double bond characterBut, C-O bond length increases by only 0.01Å suggesting C=Orelatively unaffected by rotation
planar B
Calculated Electron Populations (units-electrons)
planar
A
B
N 8.476 C 4.020 O 9.392
N 8.222
N 8.209
C 4.242
C 4.226
O 9.343
O 9.318
Amide Resonance?
A
∆ -0.254
∆ -0.267
∆ +0.222
∆ +0.206
∆ -0.049
∆ -0.074
O
N
H
HH N
HH
O
H H
O
N
HH
23-Wiberg3 4/30/91 6:03 PM
![Page 24: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/24.jpg)
Twist
Tilt
90
15-20
31
25
60260
36
16.4
17
16
10
5.52 X 10_4kOH
M-1s-1
solution high energy barrier to formation - solvent interactions on TS and products - must be due to structural changes for rehybridization at N. Twist amides don't have to rehybridize and therefore have a faster rate of hydrolysis (destabilized GS).
gas phase"barrierless"by calculation
-OH
JACS 112, 6383 (1990) R.S. Brown et.al.
Twisted Amides- Support for No Amide Resonance
N
OO
N N
O O
H NH2
O
H NH2
OHO-
N
24-BrownNoRes 4/30/91 4:07 PM
![Page 25: Bent and Twisted Amides - David A. Evansevans.rc.fas.harvard.edu/pdf/smnr_1990-1991_Lynch_John.pdf · Bent and Twisted Amides Reviews: Chem Rev 83, 549 (1983) H.K. Hall Jr., Ali El-Shekeil](https://reader030.vdocuments.us/reader030/viewer/2022040603/5e9c11aa9fe3322c3945b29b/html5/thumbnails/25.jpg)
JACS 113, 2865 (1991) Charles L. Perrin
Atomic Size Dependence of Bader Electron Populations:Significance for Questions of Resonance Stabilization
" At this time we decline to judge whether resonance is important for carboxylates and related species. Our results do not justifyany conclusions except the one that some previous objections to resonance are unfounded."
Bader electron populations (used by Wiberg) exaggerate electron density at electronegative atoms.The resulting atomic charges are judged to be unreliable, especially as evidence against resonance in carboxylate anions and related species.
25-Perrin 4/30/91 4:22 PM