Exam 2

Question 1

What does NMR give us and which electromagnetic region is seen

Answer 1

Radio waves
The specific arrangement of all carbon and hydrogen atoms in the compound

Question 2

What does IR give us and which electromagnetic region is seen

Answer 2

Infrared
The functional groups present

Question 3

What is the diagnostic region vs fingerprint region in IR spectroscopy?

Answer 3

Diagnostic region will tell us the functional groups. The fingerprint region is below 1500 and we dont care when is there

Question 4

What is the range for:
Halides?
Alkanes?
Double bonds?
Triple Bonds?

Answer 4

Double bonds 1600-1850
Triple bonds 2100-2300
Alkanes/Halides 2700-4000

Question 5

What does this splitting patter represent?

Answer 5

Ethyl

Question 6

What does this splitting patter represent?

Answer 6

Isopropyl

Question 7

What does this splitting patter represent?

Answer 7

Tert-butyl

Question 8

How can you find integration?

Answer 8

Divide all integration values by the lowest one listed. This gives the H ratio for the signals. If .5, x2

Question 9

What is the rule for multiplicity?

Answer 9

N+1

Question 10

What is indicated by a multiplet appearing between 6-8 ppm?
what about a double doublet?

Answer 10

Benzene ring

double doublet indicates Para substituted benzene.

Question 11

Steps to interpreting H NMR

Answer 11

Find degrees of unsaturation (4+ suggests a ring)
Find how many signals
Determine integration (divide by lowest #)
Determine multiplicity and neighbors (N+1 rule)
Look for known patterns (rings, TB, IsoP, ethyl)
Assemble gathered information

Question 12

What are the four things to know about Meso compounds

Answer 12

Must have 2 or more chiral centers
Contains an Internal plane of symmetry which makes is superimposable on its mirror image
Mesos are optically inactive
Stereochemistry should cancel out: L and R are present

Question 13

When would you use fractional distillation?

Answer 13

If boiling points are similar or intermolecular forces are present.

Question 14

When would you use simple distillation?

Answer 14

When two liquids have very different boiling points and little intermolecular forces.

Question 15

what makes something chiral?

Answer 15

the carbon has 4 different groups

Question 16

Chair conformations are most stable when the heavier/bulkier group is ______

Answer 16

equatorial- will have less steric hinderance.

Question 17

Lowest energy conformation is usually ___ while highest energy conformation is ______. Intermediates tend to be ____

Answer 17

Lowest- staggard with larger groups antiperiplanar
Highest- eclipsed with larger groups over each other
Intermediate-Guasch interactions

Question 18

Meso compounds

Answer 18

have internal plane of symmetry, at least 2 chiral centers, are optically inactive