Question

Using the spectra data below, which structure best matches this data? c4h8o 1h nmr triplet at 1.05 ppm (3h) singlet at 2.13 ppm (3h) quartet at 2.47 ppm (2h) ir spectrum: there is a strong peak near 1700 cm-1.

Answer 1

Answer:

Butan-2-one

Explanation:

1. 1700 cm⁻¹

A strong peak near 1700 cm⁻¹ is almost certainly a carbonyl (C=O) group.

2. Triplet-quartet

A triplet-quartet pattern indicates an ethyl group.

The 2H quartet is a CH₂ adjacent to a CH₃. The peak normally occurs at δ 1.3, but it is shifted 1.2 ppm downfield to δ 2.47 by an adjacent C=O group.

The 3H triplet at δ 1.05 is the methyl group. It, too, is shifted downfield from its normal position at δ 0.9. The effect is smaller, because the methyl group is further from the carbonyl.

3. 3H(s) at δ 2.13

This indicates a CH₃ group with no adjacent hydrogen atoms.

It is shifted 0.8 ppm downfield to δ 2.13 by the adjacent C=O group.

4. Identification

The identified pieces are CH₃CH₂-, -(CO)-, and -CH₃. There is only one way to put them together: CH₃CH₂-(C=O)-CH₃.

The compound is butan-2-one.