Answer:
Here's what I get.
Explanation:
The name tells me the compound is a lactone (a cyclic ester).
1. IR spectrum
1770 cm⁻¹
Esters and unstrained lactones normally absorb at 1740 cm⁻¹.
This peak is shifted to a higher frequency by ring strain.
A five-membered lactone absorbs at 1765 cm⁻¹, and a four-membered lactone at 1840 cm⁻¹.
The compound is probably a five-membered lactone.
2. NMR spectrum
2.28 m (2H)
2.48 t (2H)
4.35 t (2H)
This indicates three CH₂ groups arranged as X-CH₂-CH₂-CH₂-Y.
The X-CH₂- and -CH₂-Y signals would each be triplets, being split by the central -CH₂- group.
The central -CH₂- signal would be a multiplet, split by the non-equivalent hydrogens on either side.
The peak at 4.35 ppm indicates that the group is adjacent to an oxygen atom ( -CH₂- = 1.3; -CH₂-O- = 3.3 - 4.5).
The peak at 2.42 ppm indicates that the group is adjacent to a carbonyl group (-CH₂-C=O = 1.8 - 2.5.
The only way to fit these pieces together is if γ-butyrolactone has the structure shown below.
Confirmation:
(a) The IR spectrum shows a carbonyl peak at 1770 cm⁻¹.
(b) The NMR spectrum matches that given in the problem.
