Dipole moments of some substituted benzaldehydes. Conformational preference of substituents ortho to the aldehyde group
Tóm tắt
The dipole moments of a number of substituted benzaldehydes are measured in benzene solution. The angle which the dipole axis of the CHO group makes with the axis of rotation of the group is determined. The observed moments of the ortho-substituted benzaldehydes are compared with the moments calculated for free rotation as well as fors-trans ands-cis orientations of the -CHO group.o-Fluorobenzaldehyde exists mostly in thes-trans conformation.o-Chloro-,o-bromo-ando-nitro-benzaldehydcs also exist in thes-trans conformation; their observed dipole moments are even lower than the values calculated fors-trans forms, indicating mutual induction of the ortho substituents. Though 2,5-dichlorobenzaldehyde is expected to have the same dipole moment as benzaldehyde, the observed moment is significantly lower due to mutual induction of the ortho substituents. 2,5-Dimethylbcnzaldehyde has, however, almost the same moment as benzaldehyde. The dipole moment ofo-methoxybcnzaldchyde is considerably higher than the values calculated for boths-cis ands-trans conformations. An explanation is given for this.o-Hydroxybenzaldehyde exists exclusively in thes-cis form due to internal H-bonding.
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Angyal S J, Morris P J, Rassack R C and Waterer J A 1949J. Chem. Soc. 2704
Baker J W and Groves L G 1939J. Chem. Soc. 1944
Baliah V and Aparajithan K 1963Tetrahedron 19 2117
Baliah V and Ganapathy K 1963Trans. Faraday Soc. 59 1794
Baliah V and Uma M 1963Tetrahedron 19 455
Baliah V and Uma M 1972Indian J. Chem. 10 395
Bell C L, Danyluck S S and Schaefcr T 1969Can. J. Chem. 47 3529
Buswell A M, Deitz V and Rodebush W H 1937J. Chem. Phys. 5 501
Calderbank K E and LeFevre R J W 1949J Chem. Soc. 1462
Clark K 1957J. Chem. Soc. 3807
Coomber D I and Partington J R 1938J. Chem. Soc. 1444
Curran B C 1945J. Am. Chem. Soc. 67 1835
DeCrauw Th 1931Rec. trac. Chim. 50 773
DeKowaleski D G and Castellano S 1969Mol. Phys. 16 567
Dhami K S and Stothers J B 1966Can. J. Chem. 44 2855
Drakenbcrg T. Jost R and Sommer J M 1975J. Chem. Soc., Perkin II 1682
Dyer J R 1969Applications of absorption spectroscopy of organic compounds (New Delhi: Prentice-Hall India) p. 91
Estok G K and Dehn J S 1955J. Am. Chem. Soc. 77 4769
Freyman R 1938Compt. Rend. 206 1812
Grimand M and Pfister-Guillouzo G 1975Org. Magn. Reson. 7 386
Lunazzi L. Ticca L, Macciantelli D and Spunta G 1976J. Chem. Soc. Perkin II 1121
Macicl G E. MclverJr J W. Ostlund N S and Pople J A 1970J. Am. Chem. Soc. 92 4506
Miller F A, Fatcly W G and Witowski 1967Spectrochim. Acta 23A 891
Pearce J N and Berhenke L F 1935J. Phys. Chem. 39 1005
Pimentai G C and McClellan A L 1960The hydrogen bond (San Francisco: Freeman) p. 189
Sato K, Fujima Y and Yamada A 1968Bull. Chem. Soc. Jpn. 41 422
Schaefer T, Salman S R and Wildman TA 1980Can. J. Chem. 58 2364
Schuster I I, Parvez M and Freyer A J 1988J. Org. Chem. 53 5819
Smallwood H M and Herzfeld K F 1930J. Am. Chem. Soc. 52 1919
Smyth C P 1955Dielectric behaviour and structure (New York: McGraw-Hill) p. 687
Vavon G and Montheard P 1940Bull. Soc. Chim. 7 551
Vogel A 1 1954Practical organic chemistry (London: Longmans, Green) p. 687
Wasylishen R and Schaefer T 1971Can. J. Chem. 49 3216
Wulf O R, Liddel U and Hendricks S B 1936J. Am. Chem. Soc. 58 2287