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STUDY OF TAUTOMERISM IN A SERIES OF MONOAZOPIGMENTS BASED ON 1-PHENYLAZO-
2-OXY-3-PHENYLCARBAMOYLNAPHTHALENE
T. Ivanova, E. Sycheva, B. Zaitsev, E. Lisitsina, E. Polyakova, K. Dyumaev
To cite this version:
T. Ivanova, E. Sycheva, B. Zaitsev, E. Lisitsina, E. Polyakova, et al.. STUDY OF TAU- TOMERISM IN A SERIES OF MONOAZOPIGMENTS BASED ON 1-PHENYLAZO-2-OXY-3- PHENYLCARBAMOYLNAPHTHALENE. Journal de Physique Colloques, 1987, 48 (C9), pp.C9- 737-C9-740. �10.1051/jphyscol:19879126�. �jpa-00227235�
STUDY OF TAUTOMERISM I N A SERIES OF MONOAZOPIGMENTS BASED O N 1-PHENYLAZO-2-OXY-3-PHENYLCARBAMOnNAPHTHE
T.M. IVANOVA, E.D. SYCHEVA, B.E. ZAITSEV, E.S. LISITSINA, E.I. POLYAKOVA and K.M. DYUMAEV
Research USSR
Institute of Organic Intermediates and Dyes, Moscow,
Tautomerism in a series of monoazopigments based on l-phenylazo- -2-oxy-3-phenylcarbamoylnaphthalene was studied by X-ray photoelect- ron spectroscopy. The ratio of integral intensities of 01s photoelec- tron peaks from oxygen atoms occurring in different states in the molecule showed the presence of two tautomeric forms, namely, azo and. quinonehydrazone isomers, and allowed the calculation of their relative contents. Contributions from the two tautomeric forms were directly affected by the nature of substituents.
Development of printing industry, paint coatings, and polymeric materials require better orange-red pigments. The most available dyes of this kind produced in high volumes are the monoazopigments.
These compounds are known for a long time, but their molecular and crystal structures are still insufficiently studied.
X-ray photoelectron spectroscopy (XPS) was successfully used for the determination of molecular structures of various organic com- pounds, including oxyazocompounds
[I].
XPS is sensitive to variations of the charge distribution on atoms, which makes it a convenient me- thod for the identification of oxygen atoms of carbonyl and hydroxyl groups C21:In thls work XPS was used to study the derivatives of l-phenyl- azo-2-oxy-3-phenylca~?bamoylnaphthalene (I
-
XIV, see below), aiming at the elucidation of the existence of tautomerism and the quantita- tive determination of the relative contents of isomers, depending on the nature of substituents in phenyl and phenylcarbamoyl molecular fragments.
o ONHQ R~
4-h
d oH-Nd ~4
-
I
-
XIVArticle published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19879126
CY-738 JOURNAL DE PHYSIQUE
R 1 =CH R ~ = ~ - o c H ~ (VI)
,
4 4 1 (VII),
4-CONH2 (VIII) ; RI =OCH3,
R~=~-ocH)3' 1 2
(1x1, 2,4,6-(CH ) (XI, 4-C1(XI); R =OC2H5, R =4-OCH3(XII), 2,4,6-
-
(CH3)3 (XIII) 7 3 3 4 4 1 (XIV).The experimental results are presented in the Table. The atomic ratio oxy en/nitrogen was calculated for all samples using the XPS data 131 ?relative photoionization cross sections were taken from Ref. 4). As can be seen from the Table, the values obtained are close to the stoichiometric ratio.
Table
Binding energies of Is levels of oxygen aizd nitrogen, oxygen/
nitrogen atomic ratio, and the fraction of azo-form in the derlva- tives of I-phenylazo-2-oxy-3-phenylcarbamoylnaphthalene
Compound Substituen s
z
Binding energy,eV Atomic ratio FractionRI R Nl s 01 s O/N of azo-
-OH =O exp. theory form, % I H H 400.2 533.2 531.0 0.80 0.67 48 I1 3 4-OCH3 400.5533.6531.3 1.00 1.00 61 111 H 2,4,6-(CH3)3400,7 533.3 531 - 6 0.81 0.67 9 4
IV H 2-C1 400.8 53307 531.7 0.69 0.67 47 V H 4-CONH2 400.5 533.8 531.6 0.92 0.75 9 5
XI1 OC2H5 4-OCH3 400.4 533.5 531.3 1.49 1-33 6 6 XI11 OC2H5 2,4,6-(CH3)3400.3 533.6 531.6 1.12 1.00 7 7 XIV OC,H, 4-C1 400.4 533.2 531.1 1.14 1.00 85
L ,
01s XPS spectrum of I-phenyiazo-2-oxy-3-phenylcarbamoylnaphtha- lene (I) is presented in the Figure (curve 1). The spectrum reveals two peaks with binding energies 533.2 and 531,O eV, which suggests the presence of two types of oxygen atoms in the molecule studied.
The constituent peaks were obtained by graphic decoivolution, with the energy resolution of 2.2 eV. According to Ref. 5, the difference of 01s binding energies for hydroxyl and carbonyl groups is about 1.5 to 2.0 eV. The 01s binding energy for 4-phenylazophenol is known to be 533.1 eV [6]. Therefore, the peak at 533.2 eV was assigned to oxygen atoms of hydroxyl groups, and the peak at 531.0 eV, to oxygen atoms of carbonyl groups.
The ratio of intensities of individual X?S peaks of one element corresponds to the relative content of atoms present in different states in the molecule studied. Theoretical ratio of tautomeric forms for the compounds I, 111, IV and VII (see able) without oxy- gen-containing substituents was determined using the ratio of integ- ral intensities of 01s peaks of hydroxyl and carbonyl oxygen atoms and was found to be described by the hyperbolic function of the type
As an example of the case where the methoxy group is pr@se~Q, curve 2 shows the 01s XPS spectrum of I-(4-methoxypheny1azo)-2-oxy- -3-(2-methylphenylcarbamoyl)naphthalene (VI). According to Ref.1,
Binding energy, eV
Figure. 01s XPS spectra. ( 1 ) for I-phenylazo-2-oxy-3-phenylcarbarno- ylnaphthalene, (2) for l-(4-metlioxyphenylazo)-2-oxy-~-(2- -methylphenylcarbamoyl)naphthalener
the 01s binding energy for methoxy group is 533.2 eV, which coincide with the 01s binding energy for the hydroxyl group. For azo compounds containing methoxy group, the hyperbolic function acquires the form a = 2x-2/(1+x). The error for the determination of per cent tautomer contents is about 5%, due to the uncertainty of graphic deconvolu- tion of the 01s E S spectrum.
The results of electron spectroscopic determination of the tau- tomer ratio for solid-state I-phenylazo-2(and 4)-naphthols [I] turn- ed out to be less reliable due to the superposition of characteris- tic lines of tautomers, which was also coilfirmed for the compounds studied in the present work.
An increase in electron acceptor properties of R~ substituents in the para position in the phenyl fragment of I-phenylazonaphthol molecules produced a noticeable growth in the fraction of azo form
(see Table).
The results obtained agree with the round-state quantum-chemi- cal calculations for the isomers studied 771.
The I V S measurements were performed on an ES-100 Ibatos spect- rometer using MgKa radiation ( h ~ = 1253.6 eV). The samples were pressed into co~per-$rid. All spectra were measured at least twice in the vacuum of 10 Torr at room temperature. CIS peak at 285.0 eV was used as the standard. The binding energies were reproduced within the accuracy of 0.2 eV. No destruction of samples under the action of X-ray radiation was observed.
C9-740 JOURNAL DE PHYSIQUE
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