H. Takashima, Kazumori Endo, Masaki Ito
Mar 1, 1999
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Journal
Journal of Molecular Structure
Abstract
Abstract The molecular structure and conformation of methyl 3-chlorobenzoate, Cl–C 6 H 4 –C(O) –O–CH 3 , were studied by gas electron diffraction. The structures optimized by MP2/6-31G** ab initio calculations were utilized as structural constraints in the data analysis. Mean vibrational amplitudes and shrinkage corrections were calculated on the basis of the vibrational spectra measured in the present study. At the temperature of 370 K, the molecule exists in a conformational equilibrium of s- trans and s- cis form in a ratio of 70(23) : 30. The following structural parameters ( r g and ∠ α ) were found for the s- trans conformer: 〈 r (C–H)〉=1.104(10) A; 〈 r (C–C) ring 〉=1.395(2) A; r (C ring –C)=1.480(13) A; r (CO) =1.209(6) A; r (C(O)–O)=1.352(8) A; r (O–C Me )− r (C(O)–O)=0.086 A (assumed); r (C–Cl)=1.741(4) A; ∠C α =C–C α =120.7(2)°; ∠C α =C–C(O)=117.3(14)°; ∠C–CO=122.2(14)°; ∠C–C–O=116.4(12)°; ∠C–O–C=114.9(19)°;∠C α –C β –Cl=120.8(17)°. Angle brackets denote averaged values and parenthesized values are the estimated limits of error (3 σ ) referring to the last significant digit.