Question

Select the correct use of the compound tms in nmr spectroscopy.a. it is a signal-to-noise enhancerb. it is an internal standard for signal strengthc. it is a commonly used solvent for samplesd. it is an internal standard for chemical shifts

Answer 1

TMS stands for Tetramethylsilane

Formula : Si(CH₃)₄

It is used as internal standard for chemical shift

In TMS all the four methyl groups are similar thus all the 12 hydrogen are chemically equivalent. They will show proton NMR at same level and which will appear as a singlet.

We have defined this singlet to be as reference set as zero.

Generally the other organic compounds show chemical shift downfield.So have positive chemical shift with respect to TMS shift.