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Reverse substituent chemical shift effects in the C-13 nmr shifts of substituted benzonitriles

✍ Scribed by John Bromilow; Robert T.C. Brownlee

Publisher
Elsevier Science
Year
1975
Tongue
French
Weight
99 KB
Volume
16
Category
Article
ISSN
0040-4039

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✦ Synopsis

There are many literature examples correlating C-13 n.m.r. substituent chemical shifts in substituted benzenes with Bsamett substituent constants.' The direction of these substituent chemical shifts has been logically explained in terms of substituent electronic properties; the electron donors resulting in upfield shifts, and the acceptors downfield. In this letter we report an example of a 'reverse' substituent chemical shift.

The Table shows the relevant substituent chemical shifts in a series of meta-and m-substituted bensonitriles having a basis set' of substituents. It is apparent from this data that the direction of the substituent chemical shift of the cyanide carbon and the adjacent ring carbon is reversed. This observation is confirmed using the Dual Substituent

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