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Substituent effects in the charge-resonance spectra of 1,1-dinitroalkane anions
Tetrahedron Letters No. 27, pp.
17-20,
1960.
Pergamon
Press
Ltd.
Printed
in
CreatBritain
SUBSTITUENT EFFECTSIN THE CHARGE-RESONANCE SPECTRA OF 1,1-DINITROALKANE ANIONS MortimerJ.RamletandDonaldJ.Glover OrganicChemistryDivision,U. S. Naval OrdnanceLaboratarg WhiteOak,SilverSpring,Maryland,U. S. A. (Received28 October1960;in revised form 29 November 1960) BALASUBRAMANIAN and Raol have recentlyreportedthatfrequencies of a?xmptionnlaximaforthell4-*
transitionof aliphaticnitro canpaundsare
rel.atedlinearlytoTaft'a C? ifatreatanentsimilartothat
of Taft and
Lewis2is appliedto accountfor C-H aud C-C hyperconjugation. We wish now relationship for the primarybands in the to recorda linearkm-s" charge-resonance spectraof l,l-dinitroalkane anions,R-C(NO,)a-, a series inwhich the non-conjugating subetituent Rhas
a pronounced
inductiveinflu-
ence an the positionof the maximum. Spectraweredeterminedusingthepotassiumsaltsinf5~10-~molar ccncentrationa in diluteaqueGlsalkaliand prwioua4 describedprecautions were takenin carryingoutallmeasurements3.Abrmrptionmsdmafora numberof suah ccmpoundefor whichcr" of R was availableor couldhe coefficients were in the order deducedare listedin TableI. Ertinctiasl of1520,OOOand allspectrashowedminimawith e =l,OOOor leaa in the
1 A. Uubamanian
a R. W.
and c. N. R. Rao, them.
Taft,Jr. and I.
C. Lewis,
1025 (1960).
Tetrahedral 2, 210 (1959).
3 M. J. &amletand L. A. ~laplaa, J. 0~. Chem,a, - 576 (1957).
17
No.27
Charge-resonancespectra of l,l-dinitroalkaneanions
18
28&300 9 ragion,80 that cmplicationadue to band overlaphad negligible influenceon the positicrms of &.
TABLE I
No.
XXXIV
V III
RC(N02)2-,
R =
d”
Ref.
Mg9CH2
-0.165
384
a
-vi9
-0.130
384
a
+Jo
-0.125
382 (384)
b (a)
-0.100
382 (383)
b (a)
381.5 (381)
b (0)
C2Hs
o.ooo
II
%
XI
CH,COCH2CH2
+0.2Ud
379
b
(CH&HCHp
+o.22e
369.5
b
CH>OOCCH2CH2
+0.255f
379
b
N02CH2CH2
+0.50
374
b
CH$H20CH2
+0.528
365
b
HOCH2
+a555
365
b
IX
C6HS
+0.600
373
b
VI
NZCCH2 + (CH&NCH2
+1.300
342.5
b
+1.90
352
0
VII X XXIX
VIII
XXIII
aPrivata aammnication,Dr.
H.Sheahhter,OhioState University. b Spectra determinedin pmaent investigation. = L. Zeldin and H. Shechter,,T.Amer. Chm. So& 39, 4708 (1957). d Estimatedby dividingvaluefor CH,COCH,by 2.8. ' R. W. Taft and I. CL Lewis,J. @, 2436 (1958). f Batimted by dividingthe valuefor C2H50CCby (2.8)'. g Estimated to be same as value for CHaOCH2. h R. W. Taft,Jr. in M. S. Newm, Steric Effects In Ortic Chemistry, John Wileyaud Sons,New York,1956,Chapter13.
Charge-resonance spectraof l,l-dinitroalkane aniona
No.27
Of the fourteendinitroalkane aniona,the &-
19
ti plot(Figure1)
showselevencanforminguiththe expreaeiclr, $,_ = (381.6- 15.25a') rnj~r
(1)
the averagedeviaticmbeingleas than 0.5 mp. Gnqmtxb vII,vIIIanazmfI,
thedeviants,allshow&8-9~1 and have in
ower thantherelation~~hipwouldpredict
a pair d non-bondedelectrormon the atunmto
camcm
the
chargedcarbon. If the expreesim ie modifiedaa follows, &
= (381.6- 15.25a* - 8.5 y) m)r,
(2)
wherey is 1.0 or 0.0 dependingcm the presenceor abeenaeof non-bmded electronson the matan,
allfmrteenpointa fit, the awrage deviation
againbeingless
FIG. I.
)r MAX RELATED TO TV*.Q - PRESENT 0 -DATA OF SHECHTER
INVESTIGATION.
20
Charge-resonancespectra of l,l-dinitroalkaneanions It is noteworthy that &
No.27
shifts hypsochromicallywith increasing
ability of the substituentto delocalize the negative charge by inductive withdrawal of the C-R electron pair in the direction of R.
This is in
marked contrast with the effect of conjugatingelectron-withdrawing substituents which generallyshift charge-resonancemaxima of carbanionsbath+ chrcaaically by providing additional"seats for the resonatingcharge"4. The preparationof the capounds listed in Table I and a more detailed account of the spectra of l,l-dinitroalkaneanions will be presented in future papers. The authors are grateful to Dr. H. Shechtar for making available unpublished informationand to Drs. L. A. Kaplan, J. C. Dacons and D. V. Sickman for helpful discussions.
4 E. A. Braude in E. A. Braude and F. C. Nachod, Determinationof Crl?anic Structures bs Physical Methods, Academic Press, New York, 1955, p. 158.
17-20,
1960.
Pergamon
Press
Ltd.
Printed
in
CreatBritain
SUBSTITUENT EFFECTSIN THE CHARGE-RESONANCE SPECTRA OF 1,1-DINITROALKANE ANIONS MortimerJ.RamletandDonaldJ.Glover OrganicChemistryDivision,U. S. Naval OrdnanceLaboratarg WhiteOak,SilverSpring,Maryland,U. S. A. (Received28 October1960;in revised form 29 November 1960) BALASUBRAMANIAN and Raol have recentlyreportedthatfrequencies of a?xmptionnlaximaforthell4-*
transitionof aliphaticnitro canpaundsare
rel.atedlinearlytoTaft'a C? ifatreatanentsimilartothat
of Taft and
Lewis2is appliedto accountfor C-H aud C-C hyperconjugation. We wish now relationship for the primarybands in the to recorda linearkm-s" charge-resonance spectraof l,l-dinitroalkane anions,R-C(NO,)a-, a series inwhich the non-conjugating subetituent Rhas
a pronounced
inductiveinflu-
ence an the positionof the maximum. Spectraweredeterminedusingthepotassiumsaltsinf5~10-~molar ccncentrationa in diluteaqueGlsalkaliand prwioua4 describedprecautions were takenin carryingoutallmeasurements3.Abrmrptionmsdmafora numberof suah ccmpoundefor whichcr" of R was availableor couldhe coefficients were in the order deducedare listedin TableI. Ertinctiasl of1520,OOOand allspectrashowedminimawith e =l,OOOor leaa in the
1 A. Uubamanian
a R. W.
and c. N. R. Rao, them.
Taft,Jr. and I.
C. Lewis,
1025 (1960).
Tetrahedral 2, 210 (1959).
3 M. J. &amletand L. A. ~laplaa, J. 0~. Chem,a, - 576 (1957).
17
No.27
Charge-resonancespectra of l,l-dinitroalkaneanions
18
28&300 9 ragion,80 that cmplicationadue to band overlaphad negligible influenceon the positicrms of &.
TABLE I
No.
XXXIV
V III
RC(N02)2-,
R =
d”
Ref.
Mg9CH2
-0.165
384
a
-vi9
-0.130
384
a
+Jo
-0.125
382 (384)
b (a)
-0.100
382 (383)
b (a)
381.5 (381)
b (0)
C2Hs
o.ooo
II
%
XI
CH,COCH2CH2
+0.2Ud
379
b
(CH&HCHp
+o.22e
369.5
b
CH>OOCCH2CH2
+0.255f
379
b
N02CH2CH2
+0.50
374
b
CH$H20CH2
+0.528
365
b
HOCH2
+a555
365
b
IX
C6HS
+0.600
373
b
VI
NZCCH2 + (CH&NCH2
+1.300
342.5
b
+1.90
352
0
VII X XXIX
VIII
XXIII
aPrivata aammnication,Dr.
H.Sheahhter,OhioState University. b Spectra determinedin pmaent investigation. = L. Zeldin and H. Shechter,,T.Amer. Chm. So& 39, 4708 (1957). d Estimatedby dividingvaluefor CH,COCH,by 2.8. ' R. W. Taft and I. CL Lewis,J. @, 2436 (1958). f Batimted by dividingthe valuefor C2H50CCby (2.8)'. g Estimated to be same as value for CHaOCH2. h R. W. Taft,Jr. in M. S. Newm, Steric Effects In Ortic Chemistry, John Wileyaud Sons,New York,1956,Chapter13.
Charge-resonance spectraof l,l-dinitroalkane aniona
No.27
Of the fourteendinitroalkane aniona,the &-
19
ti plot(Figure1)
showselevencanforminguiththe expreaeiclr, $,_ = (381.6- 15.25a') rnj~r
(1)
the averagedeviaticmbeingleas than 0.5 mp. Gnqmtxb vII,vIIIanazmfI,
thedeviants,allshow&8-9~1 and have in
ower thantherelation~~hipwouldpredict
a pair d non-bondedelectrormon the atunmto
camcm
the
chargedcarbon. If the expreesim ie modifiedaa follows, &
= (381.6- 15.25a* - 8.5 y) m)r,
(2)
wherey is 1.0 or 0.0 dependingcm the presenceor abeenaeof non-bmded electronson the matan,
allfmrteenpointa fit, the awrage deviation
againbeingless
FIG. I.
)r MAX RELATED TO TV*.Q - PRESENT 0 -DATA OF SHECHTER
INVESTIGATION.
20
Charge-resonancespectra of l,l-dinitroalkaneanions It is noteworthy that &
No.27
shifts hypsochromicallywith increasing
ability of the substituentto delocalize the negative charge by inductive withdrawal of the C-R electron pair in the direction of R.
This is in
marked contrast with the effect of conjugatingelectron-withdrawing substituents which generallyshift charge-resonancemaxima of carbanionsbath+ chrcaaically by providing additional"seats for the resonatingcharge"4. The preparationof the capounds listed in Table I and a more detailed account of the spectra of l,l-dinitroalkaneanions will be presented in future papers. The authors are grateful to Dr. H. Shechtar for making available unpublished informationand to Drs. L. A. Kaplan, J. C. Dacons and D. V. Sickman for helpful discussions.
4 E. A. Braude in E. A. Braude and F. C. Nachod, Determinationof Crl?anic Structures bs Physical Methods, Academic Press, New York, 1955, p. 158.