Acetophenone, carbonyl group frequenc

Physical properties depend upon the same types of steric effects as chemical reactivities. In both types of data the measurable phenomenon is occurring at a clearly defined active site. Thus, for the ionization of a set of phenols the active site is the OH group, while for the stretching frequency in the infrared spectrum of the acetyl group in a set of acetophenones the active site is the carbonyl group. In the case of bioactivities, steric effects in the formation of the bioactive substance-receptor site complex are frequently of great importance. In this case the entire bioactive... 

In acetophenone CgHgGOGHg, the frequency of the carbonyl group has the value 1,684 cm i which is lower than in the case of acetone 1,706 cm. This will be due to the contribution of the structure Xll thus increasing the single character of the bond. 

SO as to relieve steric interaction between the C-methyl group and C-8-H. Comparison of the frequency of the carbonyl band in the IR spectrum (broad, 1665—1670 cmwith that of 2-hydroxy-6-methyl-acetophenone (v ax 1630 cm in CHCI3) supports this conclusion. 

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