- Email: [email protected]
NH stretching bands of some hydrazine derivatives as evidence for a lone pair-bond interaction
3Pectrochimb Acta, Vol. 25A,pp. 97 to 102. PergamonPrem 1969. Printed in NorthernIreland
NH stretching bands of some hydrazine derivatives as evidence
for a lone pair-bondinteraction D.
HADLI,
J. JAN and (in part) A.
OCVIRK
University Chemical Laboratory and Institute Jo&f Stefan Ljubljana, Yugoslavia, (Received12 &for& 1968) Abstract-Monomeric N,N-dialkylhydrazines show two abnormally spaced NH stretching bands (~180 cm-l) the lower frequency one being much more intense. In half-deuterated analogs the two bands persist with only slightly smaller spacing. With phenyls replacing alkyls the spacing and the intensitydifferencearelesspronounced. Symmetrical (l,t-substituted) hydrazmes show similar phenomena. The interaction between the nitrogen lone pair and the next N-H bond is discussedas the most probable cause of these features.
the spectra of substituted hydrazines have been investigated previously [ 11, little attention has been paid to the NH stretching region. We have investigated several symmetrical and asymmetrical alkyl- and axyl-substituted hydrazines in the vapour state and various solvents along with their deuterated and half-deuterated analogs. The spectral feakures that attracted our interest are most pronounced with the hydrazines of the type (alk),N-NH,. As in other compounds containing the primary amino group two bands appear in the region above 3000 cm-l (Table 1 and Fig. 1). The frequency of the higher situated one (band A) is less than tha,t of the ALTHOUGH
Table 1. NH stretching bands (cm-l) of some hydmzine derivatives Bend B
Band A Molecule
HNa
ND,
NH(D)
NH,
NJ’,
NH(D)
g
3371
2492
3362
3190
3197
a
3363
B
g
3373 3362
2602 2602
3361
g
3371
2490
3368
S
3348
2600
(C,H,),N.NH,
8
3362
2600
3362
C,H,C,H,N*NH, (C,H,)&NH, CHaH*NHCH, C,H,NH-NHC,H, C,H,.HC =N-NH,
B s
3369 3369 3360 3389
2602 2607
3347 3346
2340 2366 2366 2336 2360 2366 2336 2360 2330 2361 2387 2340 2330 2376 2390 2400
2440
3416
2440
3312
(CH,),N-NH,
(C,H,),N*NJ&
(CH,),N.~,
Phase*
B 8
8
3427
3142 3202 3191 3149 3190 3169 3202 3139 3190 3139 3194 3237 3251 3243 3323
3196
3198
3191 3246 3263
* g = gas, 13= solution in Ccl,.
J. G. ASTON, G. 5. JANZ and K. E. RUSSELL, J. Am. Chem. Sot. 73,1943 (1951); D. W. E. G. J. JANZ and K. E. RUSSELL, J. Chem. Phys. 19,704 (1961); E. R. SEIJI+ J. L. WOOD, J. G. ASTON and D. H. Rm, J. Chem. Phy8.23, 1191 (1964).
[l]
AXFORD,
7
97
D. HADZI, J. JAN and A. GC%‘IRK
98
I
3100
I
3200
I
!
3300
3400
35W
cm-’
Fig. 1. NH
stretching bands of l,l-dibutylhydrazine: (a) normal; 60 % deuterated (solutions iu CCb, 10 mm cell).
(b) about
asymmetric stretching of the aliphatic amines [2] but this appears consistent with the difference in electronegativity between carbon and nitrogen (Table 2). However, the frequency of the other band (B) is much lower than in aliphatic amines and less Table 2. NH,
frequencies of various X-NH,
electroneg&ivity X*
X
Bt CS N 05
2.01 2.00 3.07 3.60
group
(gas values)
of VP. 3636 3422 3376 3360
% 3460 3360 3192 3297
* A. L. ALLRED and E. G. ROCHOW, J. Inorg. Nucl. Chem. 5,264 (1968). t H. J. BECHER, Spectrochim. Acta 19, 676 (1963). $ Ref. [2]. $ M. MASTJI,M. SUZUKI and C. YIJI~, J. Chem. Sot. 3968 (1904).
than it can be accounted for by the influence of electronegativity alone. The resulting separation of A and B is about 180 cm-l whereas in amines it is only about 75 cm-l [2]. In dilute solution in non-polar solvents band B shows two distinct peaks which are not separated in the vapour phase. The relative intensity of both together against band A changes on going from vapour to solution in favour of the latter band and more so with increasing the polarity of the solvent (Fig. 2). These changes are much smaller than with aliphatic amines where the intensity ratios of the symmetrical and antisymmetrical NH, vibrations are reversed on changing from vapour to solution [2]. Corresponding trends are found also with the ND, bands. However, the NHD bands in the spectra of half deuterated hydrazines do not follow the usual pattern of the amines, i.e. that the vNH(D) band is intermediate in [2] W. J. ORVILLE-THOMAS, A. E. PARSONS and C. P. OUDEN, J. Chem. Soo. 1047 (1968); H. WOLF and U. SCHB~IDT,Ber. Bunsengea. Phy.9. Uhem. 68, 136, 143, 679 (1964).
NH stretching bands of some hydra&e derivatives
99
c
b
cm -1
Fig. 2. NB str&&ing bands of I,1 dimethylhydrazine : (a) gas (1 m cell); (b) solution in cyolohexane (2 mm cell); (c) solution in CHC1, (10 mm cell); (d) solution in CC& (1Omm cell); (0) solution in dioxaue (0.2 mm oell); (f) liquid film. between the symmetrical and antisymmetrical bands. Instead of this, two NH (Table 1) and two ND bands (e.g. 2483 and 2350 cm-l in l,l-dimethylhydrazine) appear again though less spaced than in the case of the original NH, or fully deuterated ND, hydrazines. The splitting of band B which persists with the analogous band of the fully deuterated analogs does not appear in the case of halfdeuteration (Fig. 1). This suggests the origin of the doubling of band B in terms of Fermi resonance of one NH stretching vibration with the overtone of NH, bending. The fundamental of this vibration is near 1590 cm-l. In 1,ldiphenylhydrazine band B is closer to (Fig. 3) and less intense than, band A. l,l-ethylphenyl hydrazine takes an intermediate position between the dialkyl and diphenyl derivatives. The effects of deuteration and half-deuteration are similar to those in the dialkyl hydrazine series. Symmetrical hydraziues RNH-NHR also show two rather widely spaced NH bands (Table 1 and Fig. 4). Again this is more pronounced with 1,2-dimethylhydrazine than with 1,2-diphenyl hydrazine. Benzaldehyde hydrazone is of a somewhat different structural type, but shows also two bands spaced by 135 cm-l and a deuteration behaviour like in previous examples. Band A is here much stronger than band B (Table 1).
frequency
DISCUSSION
The large difference between bands A and B in symmetrical and asymmetrical hydrazines and particularly the existence of two each NH and ND bands in the halfdeuterated analogs only slightly shifted with respect to the original bands of the
100
II. HADZI, J. JAN and A. OOVIRK
I
)
3200
I
3300
3400
I
350
cm-’
Fig. 3. NH stretching bands of: (a) l,l-pentamethylenehydrazine; (b) lethyl-1-phenylhydrazine; (c) I,l-diphenylhydrazine (solutionsinCC4,lO mm cell).
corresponding NH, and ND, groups suggest that the actual frequencies of bands A and B do not originate only from vibrational coupling of two equivalent NH oscilators but rather from two NH bonds with different force constants. A simple calculation (see Appendix) shows that a reasonable difference in both NH force constants leads to good agreement between the calculated and measured frequencies. The lowering of one NH force constant appears to be connected with the interference of this bond with the lone pair on the other nitrogen atom. The strength of the interference between the lone pair and the N-H bond depends on the mutual orientation and the electron population of the lone pair orbital. The latter factor is varied by substitution with phenyls and solvent interaction. The delocalization of the charge from the lone pair into the aromatic ring reduces the interaction of the latter and the
Fig. 4. NH stretching brtnds of: (a) 1,2dimethylhydrezine (gas, 1 m cell); (b) 1,2diphenylhydrazine (solution iu CC4, 10 mm cell).
NH stretching bands of some hydra&e derivatives
101
N-H bond which is evidenced by the shift of band B to higher frequencies in phenylhydrazines. A similar effect is produced by solvents which interact with the lone pair. Carbon tetrachloride is known to be an electron acceptor in charge-transfer complexing with amines [3] and this is even more pronounced with chloroform where the proton acts as electron acceptor. The unusual intensity relation between bands A and B is also connected with the lone pair interference as it is so strongly influenced by substitution (Table 3) and the medium. Table 3. Integrated intensities of YNHbands of some hydrazine derivatives (A x lo4 mol-l 1crnmS,in Ccl,) Band A
W,H,)~~NH,
C$&eH,N-NH, (CeH,)$*~, CeH&HNNH,
o-022 0.037 0.060 O-27
Band B O-08 0.04 0.016 0.019
There are two possible approaches to understanding the weakening of one NH bond through the next nitrogen lone pair. One emerges from the calculations of electron confIgurations and rotational barriers in hydrazine and other molecules by PEDERSEN and MOROKUMA [4]. They found that in the minimum energy conformation of hydrazine (dihedral angle about 90°C) the NH bond which is closer (cis) to the lone pair orbital of the other nitrogen looses its electron density (NH1 in Fig. 5). A different mechanism has been proposed [5] to explain the low CH frequencies in some cyclic amines in which the weakened bond is trans to the lone pair orbital of the next nitrogen. The bond is weakened by charge migration from the lone pair into the antibonding orbital of the former. This effect cannot appear in Pedersen and Morokuma’s work since the configuration interaction is not included. The same possibilities for the mutual orientations of the NH bonding and antibonding orbitals, and of the N/-lone pair orbitals as in l,l-substituted hydrazines exist also in the l,l’-substituted ones as well as in benzaldehyde hydrazone. Without
‘\
CH3
Fig. 6. Illustrating the probable orientations of orbital axes in l,l-dimethylhydrazinc. [3] G. HMFLEIN, 2. Chem. 6, 305 (1965); H. WOLFF and H. E. H~PPEL, Ber. Bunsenges. Phys. Chem. 70, 874 (1966). [4] L. PEDERSENand K. MOROKTJBIA J. Chem. Phye. 46 3941 (1967). [5] H. P. HAMLOW, S. OKUDA and N. NAKACIAWA,Tetrahedron Lett. 2553 (1964).
102
D. IYLUXG,J. Jlw and A. Ocvmx
a very advanced calculation of the electronic oontlguration of substituted hydrazines and without knowledge of the actual conformation it is futile to discuss further the mechanism of weakening of one NH bond. It may actually be expected that this weakening will show up also in the spectrum of the unsubstituted hydrazine. A low frequency (about 3200 cm-l) has in fact been assigned [6] to the symmetrical NH, vibration in the a species, but the band is weak. However, there are two NH, groups interacting in hydrazine and the frequencies and intensities of the four stretching bands do not necessarily parallel those in substituted hydrazines. Acknowledgements-The authors thank the Boris Kid& Fund and the Federal ScienceFund for Gnancialaid, and Mr. F. CVEE for technical assistance.
APPENDIX A normal co-ordin$e treatment of the NH, torso was carriedout by Wilson’s GF matrix method using the valence force field. The following force constants were obtained (in mdyn/A) through an iterative procedure (the initial constants are in brackets): 6.110 (6638) k, -0.09 ( -0.09) :::r 6.832 (5.540) kcz 0.24 (0.3) lcDl 07066 (0~680) The calculated and experimental (in brackets) frequenciesare in fairly good agreement: vxs 3371, 3190 (3371, 3190) vxn 2494, 2286 (2488, 2366) f&, 1600 (1690) 8xn,, 1184 (talc. only) partioularly if it is borne in mind that the Fermi resonanceof one NH stretohing with 2v NH, was not corrected for (the experimental values are for the gas phase where the doubling of band B is only indicated by the irregularlow frequency flank). The relative potential energy distributions for the normal end the deuterated group are given below:
QI 07029 %T'lpHI
Qz
0.2834 0.7132 0.0184
Qa
0.0000 0.0003 1.0281
vxer vxnn &&
QI
0.6270 0.3767 0.0116
Qz
0.3587 0.6438 0.0124
Qs
0.0000 0.0002 1.0283
0.2943 %$I 0.0171 bs* Expetimmtal. All compounds were synthesisedand purified by proceedingsgiven in the literature (7). The compounds with higher boiling points were deuteratedby exchange with CIIsOD. The lower boiling compounds were deuterated in the form of their hydroohlorides (exchange with D,O) from which the free bases were liberated with NaOD and dried with metallic sodium at low temperature. The whole process was carried out on a vacuum line. The spectra were recorded on 8 Perkin-Elmer Mod. 521 instrument. For gas spectra an evacuated 1 m cell was used. For solutions in CC& 10 mm cells were used in order to get unassociated molecules. The absorption of the solvent et this thickness and the appearance of several bands caused difficulties in the region of the ND, bands and particularly with half deuterated compounds so that in the latter case it was not possible to measure exactly the band positions. The ND(H) frequencies are therefore not listed except for diiethylhydrasine where particulsr efforts have been made to sort out the bands. [6] J. R. DURI~, 5. F. BUSH and E. E. MERCER,J. Chem. Phye. 44,423s (1966). [7] F. W. SCWLIERand C. HANNA, J. Am. Chews. Sot. Xi, 4996 (1951); E. FISCJXER, Ann. 221, 299 (1882); Organ. Syn., Co%, Vol. II., p. 208. John Wiley (1960); J. LEICESTER and A. I. VOUEL,Reaeurclt8, 148 (1960).
NH stretching bands of some hydrazine derivatives as evidence
for a lone pair-bondinteraction D.
HADLI,
J. JAN and (in part) A.
OCVIRK
University Chemical Laboratory and Institute Jo&f Stefan Ljubljana, Yugoslavia, (Received12 &for& 1968) Abstract-Monomeric N,N-dialkylhydrazines show two abnormally spaced NH stretching bands (~180 cm-l) the lower frequency one being much more intense. In half-deuterated analogs the two bands persist with only slightly smaller spacing. With phenyls replacing alkyls the spacing and the intensitydifferencearelesspronounced. Symmetrical (l,t-substituted) hydrazmes show similar phenomena. The interaction between the nitrogen lone pair and the next N-H bond is discussedas the most probable cause of these features.
the spectra of substituted hydrazines have been investigated previously [ 11, little attention has been paid to the NH stretching region. We have investigated several symmetrical and asymmetrical alkyl- and axyl-substituted hydrazines in the vapour state and various solvents along with their deuterated and half-deuterated analogs. The spectral feakures that attracted our interest are most pronounced with the hydrazines of the type (alk),N-NH,. As in other compounds containing the primary amino group two bands appear in the region above 3000 cm-l (Table 1 and Fig. 1). The frequency of the higher situated one (band A) is less than tha,t of the ALTHOUGH
Table 1. NH stretching bands (cm-l) of some hydmzine derivatives Bend B
Band A Molecule
HNa
ND,
NH(D)
NH,
NJ’,
NH(D)
g
3371
2492
3362
3190
3197
a
3363
B
g
3373 3362
2602 2602
3361
g
3371
2490
3368
S
3348
2600
(C,H,),N.NH,
8
3362
2600
3362
C,H,C,H,N*NH, (C,H,)&NH, CHaH*NHCH, C,H,NH-NHC,H, C,H,.HC =N-NH,
B s
3369 3369 3360 3389
2602 2607
3347 3346
2340 2366 2366 2336 2360 2366 2336 2360 2330 2361 2387 2340 2330 2376 2390 2400
2440
3416
2440
3312
(CH,),N-NH,
(C,H,),N*NJ&
(CH,),N.~,
Phase*
B 8
8
3427
3142 3202 3191 3149 3190 3169 3202 3139 3190 3139 3194 3237 3251 3243 3323
3196
3198
3191 3246 3263
* g = gas, 13= solution in Ccl,.
J. G. ASTON, G. 5. JANZ and K. E. RUSSELL, J. Am. Chem. Sot. 73,1943 (1951); D. W. E. G. J. JANZ and K. E. RUSSELL, J. Chem. Phys. 19,704 (1961); E. R. SEIJI+ J. L. WOOD, J. G. ASTON and D. H. Rm, J. Chem. Phy8.23, 1191 (1964).
[l]
AXFORD,
7
97
D. HADZI, J. JAN and A. GC%‘IRK
98
I
3100
I
3200
I
!
3300
3400
35W
cm-’
Fig. 1. NH
stretching bands of l,l-dibutylhydrazine: (a) normal; 60 % deuterated (solutions iu CCb, 10 mm cell).
(b) about
asymmetric stretching of the aliphatic amines [2] but this appears consistent with the difference in electronegativity between carbon and nitrogen (Table 2). However, the frequency of the other band (B) is much lower than in aliphatic amines and less Table 2. NH,
frequencies of various X-NH,
electroneg&ivity X*
X
Bt CS N 05
2.01 2.00 3.07 3.60
group
(gas values)
of VP. 3636 3422 3376 3360
% 3460 3360 3192 3297
* A. L. ALLRED and E. G. ROCHOW, J. Inorg. Nucl. Chem. 5,264 (1968). t H. J. BECHER, Spectrochim. Acta 19, 676 (1963). $ Ref. [2]. $ M. MASTJI,M. SUZUKI and C. YIJI~, J. Chem. Sot. 3968 (1904).
than it can be accounted for by the influence of electronegativity alone. The resulting separation of A and B is about 180 cm-l whereas in amines it is only about 75 cm-l [2]. In dilute solution in non-polar solvents band B shows two distinct peaks which are not separated in the vapour phase. The relative intensity of both together against band A changes on going from vapour to solution in favour of the latter band and more so with increasing the polarity of the solvent (Fig. 2). These changes are much smaller than with aliphatic amines where the intensity ratios of the symmetrical and antisymmetrical NH, vibrations are reversed on changing from vapour to solution [2]. Corresponding trends are found also with the ND, bands. However, the NHD bands in the spectra of half deuterated hydrazines do not follow the usual pattern of the amines, i.e. that the vNH(D) band is intermediate in [2] W. J. ORVILLE-THOMAS, A. E. PARSONS and C. P. OUDEN, J. Chem. Soo. 1047 (1968); H. WOLF and U. SCHB~IDT,Ber. Bunsengea. Phy.9. Uhem. 68, 136, 143, 679 (1964).
NH stretching bands of some hydra&e derivatives
99
c
b
cm -1
Fig. 2. NB str&&ing bands of I,1 dimethylhydrazine : (a) gas (1 m cell); (b) solution in cyolohexane (2 mm cell); (c) solution in CHC1, (10 mm cell); (d) solution in CC& (1Omm cell); (0) solution in dioxaue (0.2 mm oell); (f) liquid film. between the symmetrical and antisymmetrical bands. Instead of this, two NH (Table 1) and two ND bands (e.g. 2483 and 2350 cm-l in l,l-dimethylhydrazine) appear again though less spaced than in the case of the original NH, or fully deuterated ND, hydrazines. The splitting of band B which persists with the analogous band of the fully deuterated analogs does not appear in the case of halfdeuteration (Fig. 1). This suggests the origin of the doubling of band B in terms of Fermi resonance of one NH stretching vibration with the overtone of NH, bending. The fundamental of this vibration is near 1590 cm-l. In 1,ldiphenylhydrazine band B is closer to (Fig. 3) and less intense than, band A. l,l-ethylphenyl hydrazine takes an intermediate position between the dialkyl and diphenyl derivatives. The effects of deuteration and half-deuteration are similar to those in the dialkyl hydrazine series. Symmetrical hydraziues RNH-NHR also show two rather widely spaced NH bands (Table 1 and Fig. 4). Again this is more pronounced with 1,2-dimethylhydrazine than with 1,2-diphenyl hydrazine. Benzaldehyde hydrazone is of a somewhat different structural type, but shows also two bands spaced by 135 cm-l and a deuteration behaviour like in previous examples. Band A is here much stronger than band B (Table 1).
frequency
DISCUSSION
The large difference between bands A and B in symmetrical and asymmetrical hydrazines and particularly the existence of two each NH and ND bands in the halfdeuterated analogs only slightly shifted with respect to the original bands of the
100
II. HADZI, J. JAN and A. OOVIRK
I
)
3200
I
3300
3400
I
350
cm-’
Fig. 3. NH stretching bands of: (a) l,l-pentamethylenehydrazine; (b) lethyl-1-phenylhydrazine; (c) I,l-diphenylhydrazine (solutionsinCC4,lO mm cell).
corresponding NH, and ND, groups suggest that the actual frequencies of bands A and B do not originate only from vibrational coupling of two equivalent NH oscilators but rather from two NH bonds with different force constants. A simple calculation (see Appendix) shows that a reasonable difference in both NH force constants leads to good agreement between the calculated and measured frequencies. The lowering of one NH force constant appears to be connected with the interference of this bond with the lone pair on the other nitrogen atom. The strength of the interference between the lone pair and the N-H bond depends on the mutual orientation and the electron population of the lone pair orbital. The latter factor is varied by substitution with phenyls and solvent interaction. The delocalization of the charge from the lone pair into the aromatic ring reduces the interaction of the latter and the
Fig. 4. NH stretching brtnds of: (a) 1,2dimethylhydrezine (gas, 1 m cell); (b) 1,2diphenylhydrazine (solution iu CC4, 10 mm cell).
NH stretching bands of some hydra&e derivatives
101
N-H bond which is evidenced by the shift of band B to higher frequencies in phenylhydrazines. A similar effect is produced by solvents which interact with the lone pair. Carbon tetrachloride is known to be an electron acceptor in charge-transfer complexing with amines [3] and this is even more pronounced with chloroform where the proton acts as electron acceptor. The unusual intensity relation between bands A and B is also connected with the lone pair interference as it is so strongly influenced by substitution (Table 3) and the medium. Table 3. Integrated intensities of YNHbands of some hydrazine derivatives (A x lo4 mol-l 1crnmS,in Ccl,) Band A
W,H,)~~NH,
C$&eH,N-NH, (CeH,)$*~, CeH&HNNH,
o-022 0.037 0.060 O-27
Band B O-08 0.04 0.016 0.019
There are two possible approaches to understanding the weakening of one NH bond through the next nitrogen lone pair. One emerges from the calculations of electron confIgurations and rotational barriers in hydrazine and other molecules by PEDERSEN and MOROKUMA [4]. They found that in the minimum energy conformation of hydrazine (dihedral angle about 90°C) the NH bond which is closer (cis) to the lone pair orbital of the other nitrogen looses its electron density (NH1 in Fig. 5). A different mechanism has been proposed [5] to explain the low CH frequencies in some cyclic amines in which the weakened bond is trans to the lone pair orbital of the next nitrogen. The bond is weakened by charge migration from the lone pair into the antibonding orbital of the former. This effect cannot appear in Pedersen and Morokuma’s work since the configuration interaction is not included. The same possibilities for the mutual orientations of the NH bonding and antibonding orbitals, and of the N/-lone pair orbitals as in l,l-substituted hydrazines exist also in the l,l’-substituted ones as well as in benzaldehyde hydrazone. Without
‘\
CH3
Fig. 6. Illustrating the probable orientations of orbital axes in l,l-dimethylhydrazinc. [3] G. HMFLEIN, 2. Chem. 6, 305 (1965); H. WOLFF and H. E. H~PPEL, Ber. Bunsenges. Phys. Chem. 70, 874 (1966). [4] L. PEDERSENand K. MOROKTJBIA J. Chem. Phye. 46 3941 (1967). [5] H. P. HAMLOW, S. OKUDA and N. NAKACIAWA,Tetrahedron Lett. 2553 (1964).
102
D. IYLUXG,J. Jlw and A. Ocvmx
a very advanced calculation of the electronic oontlguration of substituted hydrazines and without knowledge of the actual conformation it is futile to discuss further the mechanism of weakening of one NH bond. It may actually be expected that this weakening will show up also in the spectrum of the unsubstituted hydrazine. A low frequency (about 3200 cm-l) has in fact been assigned [6] to the symmetrical NH, vibration in the a species, but the band is weak. However, there are two NH, groups interacting in hydrazine and the frequencies and intensities of the four stretching bands do not necessarily parallel those in substituted hydrazines. Acknowledgements-The authors thank the Boris Kid& Fund and the Federal ScienceFund for Gnancialaid, and Mr. F. CVEE for technical assistance.
APPENDIX A normal co-ordin$e treatment of the NH, torso was carriedout by Wilson’s GF matrix method using the valence force field. The following force constants were obtained (in mdyn/A) through an iterative procedure (the initial constants are in brackets): 6.110 (6638) k, -0.09 ( -0.09) :::r 6.832 (5.540) kcz 0.24 (0.3) lcDl 07066 (0~680) The calculated and experimental (in brackets) frequenciesare in fairly good agreement: vxs 3371, 3190 (3371, 3190) vxn 2494, 2286 (2488, 2366) f&, 1600 (1690) 8xn,, 1184 (talc. only) partioularly if it is borne in mind that the Fermi resonanceof one NH stretohing with 2v NH, was not corrected for (the experimental values are for the gas phase where the doubling of band B is only indicated by the irregularlow frequency flank). The relative potential energy distributions for the normal end the deuterated group are given below:
QI 07029 %T'lpHI
Qz
0.2834 0.7132 0.0184
Qa
0.0000 0.0003 1.0281
vxer vxnn &&
QI
0.6270 0.3767 0.0116
Qz
0.3587 0.6438 0.0124
Qs
0.0000 0.0002 1.0283
0.2943 %$I 0.0171 bs* Expetimmtal. All compounds were synthesisedand purified by proceedingsgiven in the literature (7). The compounds with higher boiling points were deuteratedby exchange with CIIsOD. The lower boiling compounds were deuterated in the form of their hydroohlorides (exchange with D,O) from which the free bases were liberated with NaOD and dried with metallic sodium at low temperature. The whole process was carried out on a vacuum line. The spectra were recorded on 8 Perkin-Elmer Mod. 521 instrument. For gas spectra an evacuated 1 m cell was used. For solutions in CC& 10 mm cells were used in order to get unassociated molecules. The absorption of the solvent et this thickness and the appearance of several bands caused difficulties in the region of the ND, bands and particularly with half deuterated compounds so that in the latter case it was not possible to measure exactly the band positions. The ND(H) frequencies are therefore not listed except for diiethylhydrasine where particulsr efforts have been made to sort out the bands. [6] J. R. DURI~, 5. F. BUSH and E. E. MERCER,J. Chem. Phye. 44,423s (1966). [7] F. W. SCWLIERand C. HANNA, J. Am. Chews. Sot. Xi, 4996 (1951); E. FISCJXER, Ann. 221, 299 (1882); Organ. Syn., Co%, Vol. II., p. 208. John Wiley (1960); J. LEICESTER and A. I. VOUEL,Reaeurclt8, 148 (1960).