nwrcial samples of polyoxyethylene esters such as N y r j 45 (polyosyethylene stcaratcl) may contain .:he mono- and diesters as well as unwterified glycols. The 1)rol)ortion of these in a given sani1)lr and their reslionse to the test can he a.scertained by fractionating the sanil)lc~and testing the fractions as was done by Gatenood and Graham ( 5 ) . 'I'hcrefore, any broad application of the method descritied must take cognizance of the possible limitations cited. ;\dditional information gained from d a t a on saponific:ition equivalents, molecular w i g h t determinations, amine titrations, etc. will help t'o elucidate the process. Some experimentation with the 3methyl-2-benzothiazolijne hydrazone method of Sawicki et al. ( l a ) demonstrated that it too can be used for the assay of polyoxyeth:-l compound, and hydrazine. Their spectra were recorded in demountable cells, usually in capillary thickness, a,< the location of t.he C=S band was of primary concern. The purity of liquid azines was not det,ermined except' as their infrared spectra showed them to be free from carbonyl, hydroxyl, or amino groups from the reactants. S o Iihysical constants other than molar absorptivity have been measured during
Location, C=N Absorption. Table I is a compilation of measured C=?; stretching vibrat,ional frequencies for the azines studied. The table s h o w that, for aliphatic aldehydes and ketones, the C=?: vibration falls in the range 1665 to 1635 cm.-', while aromatic ring azines have their C=S absorption in the range 1630 to 1610 cm.-' Khile no specific attempt \vas made in this work to evaluate the effwt;; of structure on the locat,ion of the C=S frequency, the expected effect- of ring strain (cyclopentanone azine z1.s. azine) and electronegativity (benzaldehyde azine 2's. o-chlorohenzaldehyde azine) are evident in the resulting location of the C=S band. Intensity, C=N Absorption. T h e intensity parameter of a particular infrared absorption band is well known to be of importance in identification ye.: by infrared spectroand the molar ahsorptivity is often used a> a unit of measurement of band intensity. Since the location of the azine C=S absorption band may sometimes overlap the location of certain carbonyl absorptions, a comparison of their relat,ive absorption intensities was niadc t,o det>ermine whether significant differences in intensities might exist. In addition, intensity information has an important bearing on the fundamental properties of the bond, such as force constant and interatomic distance. Selected molar absoqitivities are presented for certain aziner, as shown in Table 11. For t,he azines in this table, the inten?:ity of the C=N absorption is seen to be from one third to nearly one half that of the parent carbonyl group. Some of the aromatic ring azines are not included in Table 11, since nieasurements of their absorptivity values were found to be unduly high. explana-
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VOL. 36, NO. 7, JUNE 1964
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ANALYTICAL CHEMISTRY
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tion for such high values appears as a probable overlap of thc, carbon-carbon ring skeletal modes occurring near 1600 cm.-‘, thereby causing an unwanted intensity increase and false value for the C=K stret,ching node intensit This is of course not the case for the a phatic and alicyclic azines in Table 11. If a molecular weight determination could be performed on an unknown or .suspect substance, the observed intensit,y difference between azine C=N and carbonyl C=O suggest,s that identification of this c h s s might be performed in this way. Spectra. Infrared absorption spectra on 18 azines accompany this text. Such y)ectra are useful in the identification of the azines and show the similarities and differences between the original carbonyl (wmpound.+ and their azine derivatives, as well as the general conformation of the C=S band t~Ilrelope. DISCUSSIOlq
.ittempts to prepare the azines of henzolihenonr and 2-chloroaceto-
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phenone were not successful; the former was found too unreactive while the latter compound reaction went to decompoui tion. Hydrazones of unsaturated aldehydes may undergo ring closure (6) to yield pyrazolines. This reaction apparently did not occur in the preparation of trans-cinnamaldehyde azine, since the spectrum shows the presence of the strong C-H deformation vibration of the cinnamaldehyde olefinic bond (trans), which would not be present if such pyrazoline rearrangement had occurred. -1lthough unfortunately not included as a part of this work, the azine derivative of cyclobutanone should provide a strong absorption band directly locat,ed a t a normal carbonyl position, as a result of ring strain on the C=S frequency. Such an event could easily be confused by an inexperienced worker, and the band incorrectly identified as a carbonyl group. This could conceivably occur also with the cyclopentanone azine absorption which lies at. a locsation not inronsistent with some
carbonyl frequencies. The presen work should provide infrared spectros copists with a t least Pome hecond thoughts when confronted by identifications of unknown compounds, particularly whenever background information on the material is sketchy or onnexistent . LITERATURE CITED
(1) Bellamy, L. J., “The Infrared Spectra of Complex Molecules,” 2nd ed., p. 270, Methuen & C o , Ltd., London, 1958. ( 2 ) Blout, E. R., Fields, 1L2Karplus, R., J . Am. Chem. SOC.70, 194 (1948). (3) Colthup, E.B., J . Opt. SOC..Ani. 40, 397 119501. (4) Fabian, J., Legrand, ?*I., Bull. SOC. Chivi. France 1956, p 1461. ( 5 ) Fabian, J., Legrand, bI., Poirier. P.. I b i d . , p 1499. (6) Fuson, R C . “Advanced Organic Chemistry,” p. 37sj Wiley, N . Y.: h%. ( i )Suydam, Fred H., ANAL. CHEM.35, 193 (1063). RECEIVED for review January 16, 1964. Accepted March 23, 1964. Presented in part at the Sixth Annual Rocky Llountain Spectroscopy Conference, August 12, 1963, Denver, Colo.
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