Question

explain why NMR spectrum of benzene is observed at a lower field whereas that of acetylene is observed at a higher field strength​

Answer 1

Answer:

ok

Explanation:

Answer 2

Answer:

NMR spectrum of benzene is observed at a lower field whereas that of acetylene is observed at a higher field strength​ because of anisotropic effect which produce due to the circulation of  π- electrons.

Explanation:

• In NMR spectrum the protons with small value of chemical shift lie in higher field and those with high value of chemical shift lie in lower field.

• The benzene hydrogens are said to be lower field because of diamagnetic anisotropy of the ring. Anisotropic field is non uniform. An applied magnetic field is anisotropic in the vicinity of a benzene because of labile electrons in the ring interact with the applied field. The protons of benzene lie at periphery of ring where the lower field zone is present. It is the anisotropic effect which gives chemical shift to benzene protons greater than expected.

• In the acetylene, the magnetic field is generated by the circulation of π- electrons but the protons of acetylene lie in the center i.e. shielding zone. Therefore the protons of acetylene has small value of chemical shift and they lie in higher field.