Which of the patterns (A, B, C or D) fits best with the ¹³C NMR spectrum of TiCl₃(CDH₂) [Given: ¹J (C-H)> ¹J (C-D)]

Correct option is B

​​​Nuclear magnetic resonance (NMR) spectroscopy is a resonance technique involving absorption of radiofrequency energy. The magnetic environment of a nucleus affects its resonance frequency and allows structural information to be deduced. NMR-active nuclei, particularly those with a spin quantum number of 1/2, are of great significance in NMR spectroscopy. Examples include¹H,¹³C,¹⁵N, and³¹P.

​Spin-spin coupling

Structural assignment is often helped by the observation of the spin–spin coupling, which gives rise to multiplets in the spectrum due to interactions between nuclear spins. Spin–spin coupling arises when the orientation of the spin of a nearby nucleus affects the energy of another nucleus and causes small changes in the location of the latter’s resonance. A multiplet of 2I+1 lines is obtained when a spin-1/2 nucleus (or a set of symmetry-related spin-1/2 nuclei) is coupled to a nucleus of spin I. The coupling of the nuclear spins of different elements is called heteronuclear coupling. Homonuclear coupling between nuclei of the same element is detectable when the nuclei are in chemically inequivalent locations.

The coupling constant, J (usually in frequency units, Hz) is a measure of the interaction between a pair of protons. In a vicinal system of the general type, H_a-C-C-H_b then the coupling of H_a with H_b, J_ab, MUST BE EQUAL to the coupling of H_b with H_a, J_ba , therefore J_ab = J_ba.

The diagram below shows the Pascal's triangle:

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