Question

which compound will give positive Tollen's test?
a]pentanoic acid
b]2_pentanone
c]pentanal
d]3_pentanone

Answer 1

aldehydes give + ve tollens test

Answer 2

tollen's test is based on oxidation of the org. compound.

so, the compound which can be oxidised, will give tollens test.
ketone and carboxylic acids can't be oxidised as they have no hydrogen to loose (another way to define oxidation- removal of hydrogen) but aldehydes have a hydrogen attached which can be lost. s, aldehyde will give positive tollens test

Answer 3

Tollens' reagent is a chemical reagent most commonly used to determine whether a known carbonyl-containing compound is an aldehyde or a ketone.it gives silver mirror with aldehydes which is positive result.so in above options pentanal is aldehyde so it gives positive tollen's test