The UV-spectra of substituted p-nitrobenzyl phenyl ethers in
ethanol and carbon tetrachloride were recorded. The effect of
substitution on band position and intensity is correlated with the
electronic nature of the group. The IR-spectra are analysed and the
position of certain bands ii;; dis.cussed in terms of molecular structure

A. M. G. Nassar

A. M. Hindawey

F. M. Issa

R. M. Issa

S. H. Etaiw

English

Hrčak - Portal of scientific journals of Croatia

CROATICA CHEMICA ACTA CCACAA 49 (4) 709-712 (1977) CCA-1042 YU ISSN 0011-1643 547.37:535.33.1 :535.33.3 Note Ultraviolet and Infrared Spectra of Some p-Nitrobenzyl Phenyl ·Ethers A. M. G. Nassar, A. M. Hindawey, S. H. Etaiw*, R. M . Issa*, and F. M . Issa Chemistry Department, Faculty of Science, 'Alexandria University, Alexandria, and *Tanta University Egypt . ' . Received January 13, 1977 The UV-spectra of substituted p-nitrobenzyl phenyl ethers in ethanol and carbon tetrachloride were recorded. The effect of substitution on band position and intensity is correlated with the electronic nature of the group. The IR-spectra are analysed and the position of certain bands ii;; dis.cussed in terms of molecular stru-cture. · ·· INTRODUCTION The UV-spectra of nitrobenzenes have been the subject of 'many-· in-vestigations1-4. We have recently reported the electronic absorption spectra of some p-nitrobenzyl derivatives5• The present investigation is devoted to the study of UV- and IR-spectra of some p-nitrobenzyl phenyl ethers. Assignment of bands due to C. T. or to local excitation are studied. The important b.ands in the IR-spectra especially the nitro group were found to be sensitive to electronic nature of the substituent in the phenyl group. EXPERIMENTAL The p-nitrobenzyl phenyl ethers were prepared according to the method of Reid6, and have the general_formula: o,N-0-CH,o~ x X = H(I), p-CH3(II), p-Cl(III), p-Br(IV), p-CHO(V), p-N02(VI), and o-N02(VII). The UV-spectra were recorded on a UNICAM SP-800 spectrophotometer using 1 cm matched silica cells. The IR-spectra were measured on a UNICAM SP-200 spectrophotometer using KBr disc technique. RESULTS AND DISCUSSION The UV-spectra of the p-nitrobenzyl phenyl ethers in ethanol comprise three main absorption bands in the 210-325 nm region, while the spectrum of the unsubstituted compound (I) shows only two bands at 216 and 273 nm. The broad band near 270 nm resembles that observed in the spectra of nitrobenzenes3•4• It could be considered as a complex band corresponding to 710 A. M. G . NASSAR ET AL. 1La +- 1A transition of the phenyl ring and an intramolecular charge transfer (C. T.)1 from the highest occupied orbital of the phenyl ring to the lowest un-occupied orbital of the nitro-group. TABLE I UV-Spectra Obtained in Ethanol and Carbon Tetrachloride Solutions• "O Ethanol CC14 i:: ;:l lLa 1Lb+(C. T.)1 (C. T .)2 1Lb+(C. T\ (C. T .) 2 0 0. El 0 Amax. },max. Amax. J'max. u 8max. Emax. Emax. 8max. 8max. I 216 0.64 273 1.05 - - 270 1.37 -II 222 0.85 269 0.91 280 0.74 270 1.49 -III 227 1.43 269 1.20 288 0.81 266 1.35 289 IV 227 1.50 268 1.31 289 0.77 265 1.32 291 v 219 1.78 276 3.03 284b 2.80 270 s 282b 290 2.27 290 VI 220 0.84 264 0.92 300 1.37 - - 288 VII 218 1.35 263 1.27 324 0.25 - - 319 a A..n •• in nm; tmu in mo1-1 cm·t X 10-•, S saturated solution used ; - not apparent. b " - "* transition of the C = 0 group. Amax. --0.75 0.55 s s s s A support for the C. T. origin of the band could be obtained from the cal-culation of the energy of C. T. in CC14 solutions5, where the observed values agreed well with the calculated ones, except for compounds (II), (VI) and (VII). This could be attributed to strong antagonism through the molecule since the phenyl group acts mainly as a donor in this case with respect to the nitro group. Compound I II III IV v VI VII * Using data from ethanol. Ec.T.feV Calcd. 5.05 4.62 4.87 4.78 5.33 5.72 5.72 Obsd. 4.65 4.59 4.67 4.68 4.59 4.70* 4.72'' p-NITROBENZYL PHENYL ETHERS 711 The complexity of the substituted phenyl, XC6H4-0-CH2- , portion ren-ders the :n:- n* and (1B 2u +- 1A 1g) transition appear submerged under the more intense band, while the longer wavelength band, 280-323 nm appears as a shoulder. It is presumably of the n - n*. type involving the transition of a n-electron from the highest nonbonding molecular orbital of the oxygen atom to the lowest antibonding :n:* molecular orbital of the phenyl ring. The spectrum of the compound (V) containing a p-aldehyde group comprises four absorption bands, the new band located at 284 nm probably due to the :n: - n* transition of the C=O group. Interesting changes in the IR-spectra are those with the N02 and C-0-C stretching bands. Two strong bands were observed near 1520 and 1350 cm-1 regions, corresponding to the asymmetric and symmetric stretching vibrations of the nitro group, respectively. · The asymmetric band was found to shift to a lower frequency as the electron acceptor character of the substituent increases. On the other hand, the asymmetric and symmetric stretching vibrations of the C-0-C link observed near 1250 and 1050 cm-1, respectively, shifted to a higher frequency on increasing the acceptor character of the substituent X. In the. case of the compound (VII), the presence of an ortho-nitro group to the C-0-C link results in splitting of the ether band into two medium bands laying at 1256 and 1275 cm-1 • This doublet structure is in accordance with previous observ-ations7. TABLE II Some Important IR-Frequencies (in cm-1) of S1Lbstituted p-Nitrobenzyl Phenyl Ethers I II III IV v VI VII Assignment 1538 1525 1532 1531 1522 1520 1523 N02 asym. str. 1356 1354 1358 1354 1357 1358 1349 N02 sym. str. 1224 1245 1258 1255 1260 1270 1275 C-0 asym. str. 1256 ~ • 1012 1070 1060 1030 1042 1050 1030 C-0 sym. str. 1118 1178 1175 1176 1166 I 1180 1166 C-N str. REFERENCES 1. S. Nag a k u r a and J . Tan aka, J . Chem. Phys. 22 (1954) 236._ 2. S. Nag a k u r a, J. Chem. Phys. 23 (1955) 1441. 3. W. M. Schubert and J. Robins, J . Amer. Chem. Soc. 80 (1958) 554. 4. W. M. S chub er t, J. M. Craven, and H. Ste ad 1 y, J. Amer. Chem. Soc. 81 (1959) 2695. 5. R. M. I s s a, A. M. G. Na s s a r, A. M. Hind awe y, F. M. I s s a, and G. B. E 1 - He f n awe y, Spectrochim. Acta 31A (1975) 199. 6. E. E. Reid, J. Amer. Chem. Soc 39 (1917) 304. 7. M. D ah 1 a gar d and R. Q. Brewster, J . Amer. Chem. Soc. 80 (1958) 5861. 712 A. M. G . NASSAR ET AL. SAZETAK Ultraljubieasti i infracrveni spektri nekih p-nitrobenzil fenil etera A. M. G. Nassar, A. H. Hindawey, S. H. Etaiw, R. M. Issa, and F. M. Issa Snimljeni su ultraljubicasti spektri otopina p-nitrobenzil fenil etera u etanolu i tetraklorugljiku. Utvrdena je korelacija izmedu utjecaja supstituenata na polofaj i intenzitet apsorpcijskih vrpci i elektronske naravi· skupina. Na temelju polofaja karakteristicnih vrpci u infracrvenim spektrima analizirana je molekulska struktura. CHEM ISTRY DEPARTMENT FACULTY OF SCIENCE ALEXANDRIA UNIVERSITY ALEXANDRIA, EGYPT Prispjelo 13. s ljecnja 1977. 

Ultraviolet and Infrared Spectra of Some p-Nitrobenzyl Phenyl Ethers

Abstract

Similar works

Full text

Available Versions

Hrčak - Portal of scientific journals of Croatia

HRČAK - Portal of Croatian Scientific and Professional Journals