directive influence of substituents in the benzene ring
TRANSCRIPT
SEPTEMBER, 1953 465
DIRECTIVE INFLUENCE OF SUBSTITUENTS IN THE BENZENE RING
YATENDRA PAL VARSHNI University of Allahabad, Allahabad, India
SEVERAL empirical rules have been proposed from time to time to explain the directive effect of the existing group on an incoming group. Some of the important, ones are those of Crum Brown and Gibson,' T'o~lander,~ and Hammick and I l l i ng~or th .~
A new rule has been found hy the author which is based on the group number in the periodic table of the elements. The rule can be stated as follows:
If the total of the group numbers (in the periodic table) of the constituent atoms of the existing group is 1 , 7, or 13, the group will have ortho-para directing in- fluence, in all other cases meta. The group number of an alkyl radical is to be taken as 1.
The following examples illustrate the above rule. CHICO group: Adding the group numbers of the
alkyl radical and the various atoms we get (1 + 4 + 6) = 11. It,s influence will thus be meta directive.
CRUM BROWN~A., AND J. GIBSON,J. Chem. Soe., 61,367(1892). V O R ~ N D N R , A m . , 320,122 (1902).
a HAMMKK AND I L L I N ~ ~ O R T H , J. Chem. Soc., 1930, 2358.
NH2 group: Adding the group numbers of the various atoms we get (5 + 2) = 7. By the above rule its in-
Predicted Observed Eziatim orour, Suv~. influence influence " " .
R, Na, K 1 Ortho-para Orthn-pars C1, Br, I, OH, OR, NH,> XHR,
NR2 i Ortho-para Ortho-para CHICI, CHISHl 13 Orbho-I)WR Ortho-p&r& CCI,, SOSH 25 Xletn Meta KO3, C:OOH, COOR, CONH? 17 Meta hIrta CH,CO, CHO, Colt 11 >lets Mrta C S 9 Mets \Ieta COCO?H 2 i Neta Met,a, C H X h 23 \let% Met,& NIWI, S R C I 15 Xleta Met8
fluence mill he ortho-para dirertive. The tahle shows the predicted and experimentally observed influences.
The rule does not apply to the exceptional cases like CsHsCH=CHCOOH, etc., pointed out by Holleman' and therefore suffers from the usual drawbacks. This
HOLLEMAN, A. F., Chem. Rev., 1, 187 (1925).
466 JOURNAL OF CHEMICAL EDUCATION
can, however, be used as an aid to memory, though it The author is grateful to Dr. R. D. Tewari for his cannot be said to have universal application. help and encouragement in the work.
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