Spectroscopy

Question 1

What is a base peak?

Answer 1

Peak of greatest abundance in a mass spectrum.

Question 2

What is a molecular ion peak?

Answer 2

A peak produced by an ion formed by the removal of one electron from a molecule.

Question 3

What is a M+1 peak?

Answer 3

A peak produced by a molecular ion with an increased mass due to the presence of one carbon-13 atom.

Question 4

What is a fragmentation ion?

Answer 4

A positively charged ion produced when the molecular ion breaks apart.

Question 5

What is low resolution nmr?

Answer 5

A spectrum which does not show the spin-spin splitting pattern.

Question 6

What is high resolution nmr?

Answer 6

A spectrum which does show the spin-spin splitting pattern.

Question 7

Name a solvent that would be used in NMR and why is it used?

Answer 7

Carbon Tetrachloride/CCl4 as it contains no hydrogens which make signals.

Question 8

What is the reference compound for NMR?

Answer 8

Tetramethylsilane (TMS)/Si(CH3)4

Question 9

Why is TMS used a reference compound?

Answer 9

1. Its 12 hydrogens are chemically equivalent and produce a single peak which is strong due to large number of hydrogen atoms.
2. TMS is inert, it does not interact with the molecule being tested.
3. It produces a peak on the extreme right-hand side of the spectrum.