NMR

Question 1

What is NMR a combo of?

Answer 1

A Combination of very strong mag field and radio frequency radiation

Question 2

When is there a significant nuclear spin?

Answer 2

When an atom has an odd number of nucleons (protons + neutrons)

Question 3

What are the commonest isotopes w significant nuclear spin?

Answer 3

C-13 H-1

Question 4

What is another name for H-1 NMR?

Answer 4

Proton NMR

Question 5

What does NMR stand for ?

Answer 5

Nuclear magnetic resonance

Question 6

What is resonance in NMR.

Answer 6

With a specific combination of mag field strength and radio frequency radiation a nucleus can absorb energy and rapidly spin between spin states (2 states with different energies)

Question 7

What is usually used to make NMR spectrometer?

Answer 7

Very strong super conducting electro magnet cooled to 4K by liquid helium
Radio frequencies of 100-400 MHz

Question 8

How is NMR spectroscopy used in medicine?

Answer 8

MRI scans

Question 9

What is chemical shift?

Answer 9

the change in frequency needed for resonance determined by the chemical environment especially the presence of nearby electronegative atoms

Question 10

How is NMR carried out?

Answer 10

• sample dissolved in solvent and placed sample tube with small amount of TMS
• placed in NMR spectrometer and spun to even out imperfections in the mag field

Question 11

What solvents should be used for NMR? And example solvent

Answer 11

Solvents without H-1 or C-13 as to not affect NMR spec

Commonly CDCl3 which has a C-13 peak usually filtered out by a computer before the analysis

Question 12

What is TMS?

Answer 12

TMS (tetramethylsilane) (CH3)4Si is the standard reference for NMR
Has a value of 0ppm

Question 13

What does carbon-13 NMR provide Information about?

Answer 13

Types of carbon environments present from the chemical shift

Number of different carbon environments from the numbe or peaks