Infrared Spectroscopy

Question 1

What are the bonds between atoms in a molecule able to do?

Answer 1

stretch and bend, absorbing infrared energy and creating the infrared spectrum.

Question 2

What does absorption of infrared radiation cause?

Answer 2

changes in the vibrations of a molecule (bending and stretching of bonds)

Question 3

What is IR sperctrocopy used in?

Answer 3

structure determination

Question 4

What do groups of atoms in a molecule give rise to?

Answer 4

characteristic absorption bands in the IR spectrum

Question 5

What does the interpretation of an IR spectrum, and identification of the compound responsible require?

Answer 5

the uses of correlation tables of infrared data

Question 6

What is the spectral region in IR?

Answer 6

400 to 4000 cm-1

Question 7

When are stretching vibrations most useful?

Answer 7

when assigning peaks to specific bonds

Question 8

If a carbonyl group is present, where will there be a strong absorption?

Answer 8

around 1750 cm-1

Question 9

If a carbonyl group is present what 4 types of compounds are possible?

Answer 9

Acids
Esters
Aldehydes
Ketones

Question 10

If the compound is an acid, what should you look for and why?

Answer 10

Look for a broad absorption near 3400 cm-1 due to H- bonding between O-H groups

Question 11

If the compound is an ester, what should you look for?

Answer 11

Look for C-O stretch near 1200cm-1

Question 12

If the compunds is an aldehyde/ketone, what should you look for?

Answer 12

Look for C-H stretch just below 3000 cm-1

Question 13

If the compound is an alcohol, what should you look for?

Answer 13

Look for O-H stretch near 3300 cm-1

Question 14

What does aliphatic mean?

Answer 14

straight chain/ non-aromatic