Question

Tree diagram for Ha, Hb, and Hc? 400 Hz laser used?

Hi Proton Ho Ho. H. H Chemical shift (ppm) Splitting Pattern 2.9-3 i Doublet of doublet 3.1-3.2 Doublet of doublet Doublet of doublet 6.8 Doublet 7.5 Multiplck Singlet Doublet Integration

Answer 1

Nuclear Magnetic Resonance Spectroscopy (NMR) is based on the fact that when a population of magnetic nuclei is placed in an external magnetic field, the nuclei become aligned in a predictable and finite number of orientations. Diffferent NMR machines have different magnetic field strengths which are generated by superconducting magnets. Thus in 400 MHz NMR, it refers to the frequency needed to excite protons and is not related to a laser. Stronger the magnetic field higher is the frequency and more prominent splitting patterns are observed. This also makes frequency NMR machines quite expensive and maintanence costs associated with them are higher.

A proton gives a doublet when it couples with another proton. If there are two protons in its environment, then it splits as a doublet of doublets. The splitting pattern of protons Ha and Hb will be identical. Please refer the image below for the splitting patterns. Note that J coupling constant for geminal coupled protons is 12-15 Hz, for trans coupled protons is 12-18 Hz and for cis coupled protons is 7-12 Hz. Hence the doublet of doublets for Ha and Hb protons are broader than that of Hc proton.