A compound with molecular formula C4H8O2, shows absorptions at 2500-3300 cm-1 (broad), 1720 cm-1 and at 1200 cm-1 on the IR spectrum. Propose possible structure(s) for this compound.

Butanoic Acid:

I have attached the structure of Butanoic Acid. Please refer to the attachment.

Explanation:

Solution:

First of all, we need to calculate the double bond equivalent (DBE) for the compound given:

Compound = C4H8O2

DBE = (C +1) - (H + X - N)/2

C = no. of carbons

H = no. of Hydrogen

X = no. of Halogens

N = no. of Nitrogen

DBE = (4+1) - (8/2)

DBE = 5-4

DBE = 1

It indicates the presence of 1 double bond in the possible structure.

Further structure can be identified by looking the peak values of the spectrum. So, we have,

2500 - 3300 = it indicates the presence of -COOH group

1720 = it indicates the (C=0) stretching  

1200 = It indicates the (C-O) stretching

SO, the possible structure is

Butanoic Acid:

I have attached the structure of Butanoic Acid. Please refer to the attachment.