Question

Label this NMR spectra for Benzalacetone

Spin Works 4: S26 TY PPM 7.6 7.2 6.8 6.4 6.0 5.6 5.2 4.8 4.4 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 0.8 0.4 0.0 file: ...TA\Organic Labs NMR Spectra S26.dx expt: undefined transmitter freg.: 60.148254 MHP time domain size: 4096 points width: 735.29 Hz 12.2247 ppm 0.179515 Hz/pt number of scans: 0 freq. of 0 ppm: 60.147953 MHz processed size: 16384 complex points LB: 0.100 GF: 0.0000 Hz/cm: 20.487 ppm/em: 0.34061

Answer 1

Let's see label position of proton -

Benzahacetone Label peak B HA CH H, He H HA

Label proton as A, B, C and D

# Proton A-

7.29-7.45 ppm ( 5 H , multiplet )

5 aromatic proton coupled with each other, gives complex multiplet peak at 7.29 -7.45  ppm

# Proton B -

7.64 ppm (1 H, doublet )

Vinyl proton at position B , deshielded due to anisotrophic effect of aromatic ring and Pi electron.

#Proton C -

6.53-6.80 ppm (1H , doublet )

Split up as doublet due vicinal proton and appear in the range of  6.53-6.80 ppm

# Proton D -

2.35 ppm (3H ,singlet )

CH₃ proton appears as singlet because they are well separated by carbonyl group