Comment on the nature of the trend observed in the C-O couble bond stretching fr
ID: 1019660 • Letter: C
Question
Comment on the nature of the trend observed in the C-O couble bond stretching frequencies for the saturated ketones calculated. Likewise, comment on the nature of the trend observed in the frequencies for the unsaturated cyclic ketones. Arrange the saturated and unsaturated molecules according to increasing C-O double bond stretching frequency.
cyclopropanone: 2293 cm-1, cyclopentanone: 2098 cm-1, cycloheptanone: 2056 cm-1, cyclopropenone: 2320 cm-1, cyclopentadienone: 2132 cm-1, cycloheptatrienone: 2153 cm-1
Explanation / Answer
frequency is directly proportional to wavenumber(cm-1) .
order of streching frequency :
cyclopropanone > cyclopentanone > cycloheptanone.
as the ring size increases , stearichindrance decreases , so that frequency decreases .
as the delocalisation increases , streaching frequency decreases ,
order of frequency :
cyclopropenone > cyclopentadienone > cycloheptatrienone