N,N-dialkylhydrazides and their protonated forms: Ab initio calculations and studies by physical methods

Article abstract of DOI:10.1134/S1070363209110127

RHF/6-31G(d) and MP2/6-31G(d) quantum-chemical calculations of N,N-dimethylethanohydrazide molecule and also MP2/6-31G(d) calculations of its protonated forms were performed. With the use of IR and ¹H NMR spectroscopy the series of N,N-dialkylh

Full text of DOI:10.1134/S1070363209110127

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 11, pp. 2354–2358. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © V.Yu. Gusev, T.D. Batueva, V.P. Feshin, T.Yu. Nasrtdinova, A.V. Radushev, O.A. Maiorova, V.I. Karmanov, 2009, published in
Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 11, pp. 1832–1836.
N',N'-Dialkylhydrazides and Their Protonated Forms:
ab initio Calculations and Studies by Physical Methods
V. Yu. Gusev, T. D. Batueva, V. P. Feshin, T. Yu. Nasrtdinova,
A. V. Radushev, O. A. Maiorova, and V. I. Karmanov
Institute of Technical Chemistry, Ural Branch, Russian Academy of Sciences,
ul. Akad. Koroleva 3, Perm, 614013 Russia
e-mail: cheminst@mpm.ru
Received April 23, 2009
Abstract—RHF/6-31G(d) and MP2/6-31G(d) quantum-chemical calculations of N',N'-dimethylethano-
hydrazide molecule and also MP2/6-31G(d) calculations of its protonated forms were performed. With the use
of IR and 1H NMR spectroscopy the series of N',N'-dialkylhydrazides and their salts with HCl and H2SO4 were
studied. The position of proton addition was determined. The experimental results were compared with the
calculated findings.
DOI: 10.1134/S1070363209110127
It is known that hydrazides of carbocylic acids in
O
H12
O
H11
H10
H11
H10
acid solutions are protonated with the formation of
salts [1]. It was established [2] that protonation
occurred at the β-atom N. This contradicts the results
of RHF/6-31G(d) calculations according to which the
most probable location of proton addition is the O
atom, because just this protonated form possesses the
lowest total energy as compared with other forms.
C
C
C
C
N1 H12
N1
C
H9
H9
N2
N2
C
H3
H4
H8
C
H8
H3
H4
C
H7
H7
H5
H6
H5
H6
1
2
N',N'-Dialkylhydrazides also form salts in acid
media [3, 4]. However two alkyl radicals at the β-atom
N lead to steric hindrances for its protonation and
generated by them positive inductive effect leads to the
redistribution of the electron density that may change
the relation of the total energies of protonated forms.
Therefore it was interesting to perform quantum-
chemical calculations of the molecules of N',N'-
dialkylhydrazides and of their possible protonated
forms, to compare the calculated and experimental data,
and to confront the results with those of unsubstituted
hydrazides. By analogy with unsubstituted hydrazides
it is presumable that N',N'-dialkylhydrazides may be
present in two forms (1 and 2).
1 and 2 forms. The transformation of the molecule into
form 2 with subsequent deprotonation occurs in strong
–
alkaline media (COH > 3 mol l–1) [4]. In less alkaline
solutions N',N'-dialkylhydrazides are in form 1.
RHF/6-31G(d) and MP2/6-31G(d) quantum-chemical
calculations of forms 1 and 2 of the N',N'-dimethyl-
ethanohydrazide molecule indicated that form 1 is
more favorable in energy. Its total energy is by
22.0 kcal mol–1 (RHF) or 18.3 kcal mol–1 (MP2)
smaller then that of form 2 (Table 1).
According to quantum-chemical calculations of
CH3CONHN(CH3)2 molecule by both methods the
negative charges on O and α-N atoms in form 1 are of
close value, and the charge on the β-atom N is
considerably smaller (Table 1). These results deviate
from data obtained for ethanohydrazide molecule
where the charges on O, α- and β-N atoms are nearly
equal [2].
According to the literature data [3, 4] in solids they
are in form 1. In organic solvents as it follows from 1H
NMR spectra they are also in form 1. In aqueous or
aqueous-alcoholic solvents N',N'-dialkylhydrazides,
depending on pH of the media, may be present in both
2354

N',N'-DIALKYLHYDRAZIDES AND THEIR PROTONATED FORMS
2355
Table 1. Total energies (E) of 1–5 molecules calculated at the RHF/6-31G(d) и MP2/6-31G(d) levels of theory, and charges
(q) on O and N atoms
MР2/6-31G(d)
RHF/6-31G(d)
q, e
q, e
Molecule
Е, eV
Е, eV
О
N1
N2
О
N1
N2
–9307.60
–9306.80
–9317.01
–9316.65
–9317.13
–0.62
–0.71
–0.49
–0.40
–0.65
–0.60
–0.40
–0.56
–0.66
–0.54
–0.38
–0.44
–0.51
–0.38
–0.38
–9279.88
–9278.92
–0.60
–0.70
–0.61
–0.39
–0.37
–0.44
1
2
3
4
5
Table 2. Charges on hydrogen atoms (q) calculated for the molecules 1–5 (HL) at the MР2/6-31G(d) level of theory
q, e
HL
Н3
Н4
Н5
Н6
Н7
Н8
Н9
Н10
0.20
0.25
0.23
0.27
0.30
Н11
0.20
0.19
0.29
0.28
0.26
Н12
0.37
0.46
0.42
0.46
0.45
Н13
0.19
0.16
0.27
0.22
0.21
0.14
0.16
0.25
0.20
0.18
0.17
0.16
0.25
0.25
0.23
0.18
0.16
0.26
0.21
0.21
0.18
0.16
0.26
0.25
0.23
0.14
0.16
0.25
0.20
0.18
0.19
0.19
0.21
0.24
0.26
–
1
2
3
4
5
–
0.47
0.45
0.52
MP2/6-31G(d) quantum-chemical calculations of
possible protonated forms of N',N'-dimethylethano-
hydrazide molecules 3, 4, 5 indicated that the most
favorable in energy is form 5: It is more favorable than
form 5 by 11.0 kcal mol–1 and by 2.7 kcal mol–1 than
form 3 (Table 1).
+
+
+
O
O
O
H13
H11
H10
H11
H10
H11
H10
C
C
C
C
C
C
N1 H12
N1 H12
N1 H12
H9
H9
H9
H13
C
N2
N2
N2
H13
H3
H4
H8
C
C
H3
C
H3
C
H8
H7
H8
C
H7
H4
H4
H7
H6 H5
H6 H5
H6 H5
3
4
5
Thus, as it follows from distribution of negative
charges in N',N'-dimethylethano-hydrazide molecule
and total energies of its protonated forms the most
probable is the proton addition to the O atom with the
formation of from 5. Similar relations between total
energies of possible protonated forms were also
revealed for the methanohydrazide molecule [2].
study the signal of the salt-formating proton was not
observed up to δ ~ 16 ppm. Therefore direct deter-
mination of location of addition by this method
appeared to be impossible. As will be demonstrated
below it may be only suggested from the chemical
shifts of the proton signals.
As seen from Table 2 the positive charges on
hydrogen atoms in protonated forms of N',N'-demethyl-
ethanolhydrazide molecule according to quantum-
chemical calculations are larger than in neutral
molecule. This indicates the reduction of their
shielding leading to the downfield shift of their signals
To determine the location of proton addition we
1
recorded H NMR and IR spectra of N',N'-diethylhep-
tanohydrazide (I), N',N'-diisobutylbenzohydrazide (II)
and their salts with HCl (Ia, IIa), and also N',N'-
dipentyl-2-ethylhexanohydrazide (III) and its salt with
H2SO4 (IIIa). In 1H NMR spectra of compounds under
1
in the H NMR spectra. The increase in the positive
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 11 2009

2356
GUSEV et al.
1
Table 3. H NMR spectra of N',N'-dialkylhydrazides and
It is seen that protons of NCH2 group are shifted
downfield stronger than the protons of CH2CO and
CHCO groups in compounds I and III and ortho-
protons of phenyl group of compound II. This shift
(from 0.99 to ~ 1.3 ppm) is in good agreement with the
shift of the signals of protons in the salt (CH3-)3N+ as
compared with neutral (CH3-)3N molecule (~1 ppm)
[6]. Thus as it follows from chemical shifts of protons
of NCH2 and CH2CO groups the most probable
protonated form is form 3. The signal of proton of NH
group shows a stronger downfield shift than it was
expected from the change in its positive charge. It is
probable that the location of the signal depends on the
presence of the solvent for it can form hydrogen bond
with the latter.
their salts (L)
CH2CO,
L
NH
NCH2
Ph
СНСО
5.80 s; 5.90 s 2.70 q; ~2.4 q 2.38 t; 2.06 t
–
–
I
11.99 s
3.69 br.s
2.66 d
2.44 t
Iа
6.86 br.s
–
–
7.70 d; 7.35–
7.50 m
8.25 d; 7.50–
7.65 m
–
II
14.43 br.s
3.76 br.s
IIа
III
5.95 s; 6.01 s 2.70 t
11.20 s 3.60 br.s
2.40–2.49 m;
2.93–3.00 m
2.28–2.40 m
–
IIIа
charges on hydrogen atoms in protonated forms of
N',N'-dimethylethanohydrazide molecule as compared
with neutral molecule 1 is shown bellow.
In IR spectra of all studied compounds in the region
3100–3150 cm–1 there is an absorption band of
stretching vibrations of N–H bond of the amide group,
in the region 2500–2750 cm–1 there are many bands of
stretching vibrations of N–H of R3N+H group, in the
region 1670–1690 cm–1, the absorption band “amide
I,” in the region 1540–1560 cm–1, the absorption band
“amide II.” The data of IR spectra correspond to the
molecule protonated at the β-atom N.
Molecule
3
4
5
NH
0.06
0.05
0.09
0.09
0.07
0.06
0.08
0.08
0.04
CH3CO (average value)
NCH3 (average value)
As follows from the above mentioned data, in form
3 the increase in the positive charge of the protons of
NCH3 group and hence the deshielding is greater then
that of protons of CH3CO group. In the form 5 this
relation is reversed, and in the form 4 the increase in
the positive charges on the protons of these groups is
nearly equal. Thus it is presumable that in the form 3
the signals of protons of NCH3 group would be more
shifted downfield as compared with the signals of
protons of CH3CO group, in form 5 would be a reverse
relation, and in form 4 their chemical shifts would be
similar.
Thus in N',N'-dialkylhydrazides of aromatic, ali-
phatic and branched in α-position aliphatic acids which
possess at the amine atom N two normal or branched
aliphatic radicals, protonation, as in the case of non-
substituted hydrazides, probably, also occurs at the β-
atom N.
In N',N'-dialkylhydrazides there are intermolecular
hydrogen bonds which are able to lead to redistribution
of electron density and thus to the inconsistency
between calculated and experimental results. To reveal
their influence on the distribution of electron density
we performed quantum-chemical calculations of a
dimer of N',N'-dimethylethanohydrazide (6) on the
RHF/6-31G(d) level of theory. The results are as
follows: total energy (–18560.32 eV), the charges on
atoms (q/e) – О1, О4 (-0.66); N2, N5 (–0.65); N3, N6 (–
0.38). As follows from comparison of these results
with calculated data on molecule 1 (Table 1) the
formation of intermolecular hydrogen bonds do not
lead to an essential change in the electron density on
the atom O, α- and β-atoms N. Therefore they cannot
lead to the discrepancy of calculated and observed
data. Probably the location of proton addition to the
molecules of N',N'-dialkylhydrazides is determined not
1
Table 3 presents data on H NMR spectra of N',N'-
dialkylhydrazides I–III and their salts Ia–IIIa. Double
set of signals in the spectra of aliphatic hydrazides I
and III is connected with presence in such compounds
of E,Z-tautomerism, that is in turn due to the hindered
rotation about C–N bond [5]. Salt formation leads to
the disappearence of this doubling showing the
absence of such tautomerism in salts. The downfield
shift of proton signals in salts relative to neutral
compounds I–III is as follows.
Salt
Iа
IIа
–7.57
–1.10
III
–5.25; –6.01
–0.90
NH
–6.19; –6.09
CH2CO; CHCO; Ph –0.99; ~–1.3
NCH2
–0.38; –0.06 –0.55; –0.15 ∼+0.1; ~+0.6
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 11 2009

N',N'-DIALKYLHYDRAZIDES AND THEIR PROTONATED FORMS
2357
only by the charges on atoms but also by other factors
which are not taken into account in the quantum-
chemical calculations.
11.56. C11H25N2OCl. Calculated, %: С 55.81; Н 10.57;
N 11.84. IR spectrum (mull in mineral oil), ν, сm–1:
2490–2750 (many bands) (R3N–H)+; 1691 (amide I);
1
1546 (amide II). H NMR spectrum, (δ, ppm, J, Hz):
CH3
H3C
O1
H
N6
11.99 s (1Н, NH); 3.69 br.s (4Н, 2CH2N); 2.44 t (2Н,
CH2СО, J = 7.5); 1.60–1.70 m (2Н, СH2CH2CO); 1.36
t (6Н, 2CH3CH2N, J = 6.9); 1.28 br.s (6Н, 3СН2); 0.86
t (3Н, СН3, J = 6.6).
H3C
N5
C
C
N2
N3
O4
H
CH3
N',N'-Diisobutylbenzohydrazide (II) was prepared
by analogy with [4]. Yield 27%, mp = 99–99.5°C
(i-PrOH:H2O = 1:1). Rf = 0.78. Found, %: С 72.77,
72.69; Н 9.19, 9.15; N 11.22, 11.29. C15H24N2O.
Calculated, %: С 72.58; Н 9.68; N 11.29. IR spectrum
(mull in mineral oil), ν, сm–1: 3213 (N–H); 1648
CH3
H3C
6
EXPERIMENTAL
1H NMR spectra were recorded on a MERCURY
plus300 spectrometer (Varian, USA) in CDCl3,
internal reference HMDS. IR spectra were recorded
with the use of a Fourrier spectrometer IFS-66
(Bruker, Germany). Elemental analysis was done with
the use of a CHNS-932 analyzer (LECO Corporation,
USA). Thin layer chromatography analysis was done
on Silufol plates in the system p-xylene: BuOH (2:1),
developing with phosphomolybdic acid.
1
(amide I); 1552 (amide II). H NMR spectrum, (δ,
ppm, J, Hz): 7.70 d (2Н, Ph, J = 8.1); 7.34–7.50 m
(3Н, Ph); 6.86 br.s (1Н, NH); 2.66 d (4Н, 2CH2N, J =
7.5); 1.75 m (2Н, 2 СНCH2N); 0.96 d (12Н, 4 СН3, J =
6.6).
N',N'-Diisobutylbenzohydrazidinium chloride (IIa)
was prepared by analogy with Ia. It was recrystallized
from p-xylene. Found, %: С 63.73, 63.72; Н 8.66,
8.67; N 10.02, 10.01. C15H25N2OCl. Calculated, %: С
63.27; Н 8.79; N 9.84. IR spectrum (mull in mineral
oil), ν, сm–1: 3106 (N–H); 2540–2775 (many bands)
Quantum-chemical calculations of N',N'-dimethyl-
ethanohydrazide molecule and its protonated forms
were done with full geometry optimization on the
RHF/6-31G(d) and MP2/6-31G(d) levels of theory
using Gaussian 03W computer program [8].
1
(R3N–H)+; 1672 (amide I); 1542 (amide II). H NMR
spectrum, (δ, ppm, J, Hz): 14.43 br.s (1Н, NH); 8.25 d
(2Н, Ph, J = 7.2); 7.50–7.65 m (3Н, Ph); 3.76 br.s (4Н,
2CH2N); 2.19 m (2Н, 2СНCH2N); 1.11 d (12Н, 4 СН3,
J = 6.6).
N',N'-Diethylheptanohydrazide (I) was prepared
by analogy with [4]. Viscous yellow liquid thus
formed was distillated at 179–184°C (11 mm Hg). The
product crystallized at storage. Yield 62.5%, mp = 39°C.
Rf = 0.67. Found, %: С 65.16, 65.13; Н 12.07, 12.22;
N 13.74, 13.75. C11H24N2O. Calculated, %: С 66.0; Н
12.0; N 14.0. IR spectrum (mull in mineral oil), ν, сm–1:
3216 (N-H); 1668 (amide I); 1554 (amide II). 1H NMR
spectrum, (δ, ppm, J, Hz): 5.90, 5.80 (both 1Н, NH, Z-
and Е-isomer, respectively); 2.70 q (2.5 Н, CH2N, Е-
isomer, J = 7.2); 2.36-2.48 m (2.75 Н, CH2N, Z-
isomer, CH2СО, Е-isomer); 2.06 q (0.75 Н, CH2СО, Z-
isomer, J = 7.8); 1.5–1.62 m (2Н, СH2CH2CO); 1.24
br.s (6Н, 3CH2); 1.02 t (J = 7.2), 1.00 t (J = 7.2) (6Н, 2
CH3CH2N); 0.82 t (3Н, СН3, J = 6.3).
N',N'-Diamyl-2-ethylhexanohydrazide (III) was
prepared from 2-ethylhexanohydrazide and double molar
quantity of pentyl bromide in the presence of KOH at
boiling during 15 h in the isopropyl alcohol with
addition of benzene for the azeotropic distillation of
water. After separation of precipitate of potassium
bromide and alcohol distillation the solid precipitate
thus formed was dissolved in chloroform, washed by
water and sodium carbonate solution. The chloroform
was distillated off and the product thus formed was
recrystallized. Yield 62%, mp = 75–75.5°С (acetone:
H2O = 3:1). Found, %: С 72.47, 72.60; Н 12.73, 12.59;
N 9.38, 9.31. C18H38N2O. Calculated, %: С 72.36; Н
12.73; N 9.38. IR spectrum (mull in mineral oil), ν,
сm–1: 3240 (N–H); 1654 (amide I); 1552 (amide II). 1H
NMR spectrum, (δ, ppm, J, Hz): 5.95, 6.01 both s (1Н,
NH); 2.93–2.99 m (0.5Н, СНСО); 2.70 t [3.75Н,
(CH2)2N, J = 7.5]; 2.40–2.49 m [0.75Н, (CH2)2N,
CHСО]; 1.63 m (4Н, 2NСН2СН2С3Н7); 1.48 m (4Н,
N',N'-Diethylheptanohydrazidinium chloride (Ia)
was prepared by passing gaseous HCl through the
solution of 2',2'-diethylheptanohydrazide in chloroform
during 1.5 h. The product was separated by chloroform
evaporation. It was used without further purification.
Found, %: С 55.37, 55.48; Н 10.46, 10.38; N 11.54,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 11 2009

2358
GUSEV et al.
3. Gusev, V.Yu., Baigacheva, E.V., Radushev, A.V., and
Batueva, T.D., Zh. Prikl. Khim., 2007, vol. 80, no. 10,
p. 1744.
СН2С3Н7, CH2СН3); 1.27 m [12Н, СН2(СН2)2СН3,
2N(СН2)2(СН2)2СН3]; 0.86 m [12Н, 4СН3 (Bu, 2Am,
Et)].
4. Gusev, V.Yu, Radushev, A.V., Verkholantseva, T.A.,
and Batueva, T.D., Izv. Akad. Nauk. Ser. Khim., 1996,
no. 11, p. 2645.
N',N'-Diamyl-2-ethylhexanohydrazidinium sulfate
(IIIа) was prepared by shaking 0.05 mol l–1 solution of
N',N'-dipentyl-2-ethylhexanohydrazide in kerosene
with an equal volume of 0.5 mol l–1 sulphuric acid
during 10 min. The precipitate thus formed was
filtered off and dried. It was used without additional
purification. Found, %: С 56.88, 56.61; Н 10.49,
10.77; N 7.04, 7.05. C18H40N2O5S. Calculated, %: С
54.55; Н 10.10; N 7.07. IR spectrum (glass from KBr),
ν, сm–1: 3150 (N-H); 2770-2620 (many bands) (R3N–
H)+; 1684 (amide I); 1547 (amide II); 1217, 1177
5. Bouchet, Ph., Elguero, J., Jacquier, R., and Pereillo, J.-M.,
Bull. Soc. Chim. Fr., 1972, no. 6, p. 2264.
6. Pretsch, E., Bullmann, P., and Affolter, C., Structure
Determination of Organic Compounds: Tables of
Spectral Data, 3nd ed., Heidelberg: Springer, 2000.
7. Evans, R.F. and Kynaston, W., J. Chem. Soc., 1963,
May, p. 3151.
8. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuse-
ria, G.E., Robb, M.A., Cheeseman, J.R., Montgo-
mery, J.A., Jr., Vreven, T., Kudin, K.N., Burant, J.C.,
Millam, J.M., Iyengar, S.S., Tomasi, J., Barone, V.,
Mennucci, B., Cossi, M., Scalmani, G., Rega, N.,
Petersson, G.A., Nakatsuji, H., Hada, M., Ehara, M.,
Toyota, K., Fukuda, R., Hasegawa, J., Ishida, M.,
Nakajima, T., Honda, Y., Kitao, O., Nakai, H.,
Klene, M., Li, X., Knox, J.E., Hratchian, H.P.,
Cross, J.B., Bakken, V., Adamo, C., Jaramillo, J.,
Gomperts, R., Stratmann, R.E., Yazyev, O., Austin, A.J.,
Cammi, R., Pomelli, C., Ochterski, J.W., Ayala, P.Y.,
Morokuma, K., Voth, G.A., Salvador, P., Dannen-
berg, J.J., Zakrzewski, V.G., Dapprich, S., Daniels, A.D.,
Strain, M.C., Farkas, O., Malick, D.K., Rabuck, A.D.,
Raghavachari, K., Foresman, J.B., Ortiz, J.V., Cui, Q.,
Baboul, A.G., Clifford, S., Cioslowski, J., Stefanov, B.B.,
Liu, G., Liashenko, A., Piskorz, P., Komaromi, I.,
Martin, R.L., Fox, D.J., Keith ,T., Al-Laham, M.A.,
Peng, C.Y., Nanayakkara, A., Сhallacombe, M.,
Gill, P.M.W., Johnson, B., Chen, W., Wong, M.W.,
Gonzalez, C., and Pople, J.A., Gaussian 03, Revision
D.1. Gaussian, Inc. Wallingford, CT, 2005.
1
(νaS=O); 1060, 1040 (νsS=O). H NMR spectrum, (δ, ppm,
J, Hz): 11.20 br.s (1Н, NH); 8.43 br.s (1Н, НSO4–); 3.60
br.s [4Н, (CH2)2N]; 2.28–2.40 m (1Н, CHСО), 1.74 m
(4Н, 2NСН2СН2С3Н7); 1.52 m (4Н, СН2С3Н7,
CH2СН3); 1.30 m [12Н, СН2(СН2)2СН3, 2N(СН2)2
(СН2)2СН3]; 0.86 m [12Н, 4СН3 (Bu, 2 Am, Et)].
ACKNOWLEDGMENTS
The work was financially supported by the Russian
Foundation for Basic Research (grant 08-03-00163-а).
REFERENCES
1. Grekov, A.P. and Veselov, V.Ya., Physical Chemistry
of Hydrazine, Kiev: Naukova Dumka, 1979.
2. Feshin, V.P., Kon’shin, M.Yu., Radushev, A.V.,
Feshina, E.V., Gusev, V.Yu, Lesnov, A.E., and
Karmanov, V.I.., Izv. Akad. Nauk. Ser. Khim., 1996,
no. 11, p. 2645.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 11 2009