For the protons labeled Ha and Hb in the structure below, predict the characteri

Question

For the protons labeled Ha and Hb in the structure below, predict the characteristics of their signals in the H NMR spectrum: the approximate chemical shift, the splitting pattern, and the integration value. Approximate Integration Splitting chemical shift value H NMR signal O 1 ppm O 1H O singlet for H O 2H O 2 ppm O doublet O 3-5 ppm O 3H O triplet O 5-6 ppm 4H O quartet O 7-8 ppm O 5H O quintet O 6H H H O multiplet H NMR signal O 1 ppm O 1H O singlet for H O 2 ppm O 2H doublet O 3-5 ppm O 3H O triplet O 5-6 ppm O quartet. 4H O 7-8 ppm O 5H quintet O 6H O multiplet

Explanation / Answer

The details of 1H-NMR are as follows,

Ha ...........3-5 ppm.................quartet.....................2H

Hb ...........2 ppm.................triplet.....................2H

Ha protons are next to an oxygen (electronegative) and thus its position shifts downfield in the NMR spectrum appearing around 3-5 ppm. It has a CH3 as neighbour, and thus shows splitting pattern of a quartet for 2H.

Hb protons are next to a carbonyl C=O, thus appears at 2 ppm. It has an CH2 as a neighbour and therefore shows splitting pattern of a triplet for 2H.

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