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Grade 12Physical Chemistry

why formaldehyde is more reactive than benzeldehyde?

Profile image of krishna  singh pal
13 Years agoGrade 12
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2 Answers

Profile image of Sushma C.
13 Years ago

benzene ring due to the delocalization of electrons decreses the charge on carbonyl carbon, ehich decreases the reactivity of benzaldehyde. where as in formaldehyde the -h groups attached to the carbonyl carbon get a highly positive change and thus more reactive than that of benzaldehyde.

Profile image of sounak sinhababu
7 Years ago
Formaldehyde has a H- (Hydrogen) attached to the Carbonyl carbon of -CHO (aldehyde) group.
Whereas , Benzaldehyde has a Ph- (Phenyl) group attached.
The major reactions of aldehydes are Nucleophilic addition reactions(NAR)[ in which a nucleophile gets added to the Carbonyl carbon which is electropositive in nature].
Addition of a Nucleophile depends on Steric Factor.
The less sterically hindered the Carbonyl carbon is , greater is the ease of addition of Nucleophile.
 
In case of Benzaldehyde and Formaldehyde , Benzaldehyde has a more sterically hindered carbonyl carbon (due to bulkier Ph- group) as compared to Formaldehyde (with a smaller H- group). Thus , Nucleophilic reactions takes place faster in case of Formaldehyde.
Therefore , Formaldehyde is MORE REACTIVE TOWARDS NUCLEOPHILIC ADDITION REACTIONS than Benzaldehyde.