IR

Question 1

What vibrations do the peaks observed in an infrared spectrum with frequencies > 1500 cm-1 correspond to?
a specific functional group
a specific bond
a specific molecule

Answer 1

a specific bond

Question 2

What is the crystal on the center of the sample plate of the IR made of?

diamond
ruby
emerald

Answer 2

diamond

Question 3

What must you do to a solid sample BEFORE you take the IR spectrum of the solid sample?
dissolve it with water
pack it into a pile
crush it
make it a paste

Answer 3

crush it

Question 4

What must you do to the solid sample AFTER they have been placed on the IR spectrometer?
apply pressure to it
blow on it
air it out
apply liquid to it

Answer 4

apply pressure to it

Question 5

When taking the IR spectrum of a liquid sample, how many drop(s) of liquid should you use?
1
2
3
4

Answer 5

1

Question 6

When assigning a peak in an infrared spectrum, what should you assign it to?
a specific functional group
a molecule
a specific bond and a functional group it is part of

Answer 6

a specific bond and a functional group it is part of

Question 7

How many peaks in an IR spectrum would you expect to see that would characterize a carboxylic acid functional group?
1
2
3
4

Answer 7

2

Question 8

How many peaks in an IR spectrum would you expect to see that would characterize an alcohol functional group?
1
2
3
4

Answer 8

1

Question 9

IR spectra can be measured by passing IR radiation through a sample or by reflecting IR radiation off a sample. Which of these 2 methods will you use in your lab?
passing IR radiation through a sample
reflecting IR radiation off a sample

Answer 9

reflecting IR radiation off a sample

Question 10

What kind of artifacts does the background scan remove from the IR spectrum?
IR absorptions due to atmospheric water
IR absorptions due to atmospheric carbon dioxide
instrument artifacts
all of the above

Answer 10

all of the above

Question 11

Match the peaks (in cm^-1) with the appropriate bond and functional group.

3350 cm ^-1 =
2800-3000 cm ^-1 =

Answer 11

3350 cm ^-1 = O-H alcohol
2800-3000 cm ^-1 = csp3-H carbon alhyl

Question 12

2900 - 3000 cm^-1 =
2716 - 2817 cm^-1 =
1720 cm^-1 =

Answer 12

2900 - 3000 cm^-1 = Csp3-H
2716 - 2817 cm^-1 =c-h ALDEHYDE
1720 cm^-1 = C=0 aldehyde

Question 13

2800 - 3000 cm^-1
1710 cm^-1

Answer 13

2800 - 3000 cm^-1 = CSP3-H
1710 cm^-1 = C=0 KEYTONE

Question 14

Which of the following is/are possible causes for the weak signals observed.
A. Crystals were not ground finely enough
B. Not enough pressure on the sample on top of the diamond crystal
C. Baseline was not run correctly
D. Diamond crystal is not clean
Both A and B are possible
Both C and D are possible

Answer 14

Both A and B are possible

Question 15

A student ran an IR spectrum of a liquid shown in A below, that had a strange feature indicating >100% transmission. The student realized that they had forgotten an important step, and after re-running the spectrum with the important step obtained spectrum B. What do you think the important step was that the student forgot first time
A. Crystals were not ground finely enough
B. Not enough pressure on the sample on top of the diamond crystal
C. Baseline not run correctly
D. Diamond crystal not clean
Both A and B are possible
Both C and D are possible

Answer 15

Both C and D are possible