Orgo Samples

Question 2

What is the prefix for carbon chains consisting of:

• 1 carbon?
• 2 carbons?

Answer 2

• 1 carbon = “meth-“
• 2 carbons = “eth-“

Question 12

How does the boiling point of methanol compare to that of water?

Answer 12

Water has a higher boiling point than methanol.

Both water and methanol can undergo hydrogen bonding. However, each water molecule has two hydrogens bound to the oxygen, thus it can undergo twice as many hydrogen bonds per molecule, increasing the intermolecular attractive force and the boiling point.

The BP of water is 100°C, that of methanol is 65°C.

Question 13

What functional group yields the IR peak shown below?

Answer 13

This IR peak corresponds to a amine (N-H) functional group.

Amine groups always give a sharp absorption peak in the range of 3100-3500 cm^-1.

Question 15

What is the principal functional group in this molecule?

Answer 15

The -OH group is the principal functional group.

In general, oxygen-containing groups take priority in nomenclature, and the more bonds to oxygen in the functional group, the higher its priority. This molecule, 1-amino-2-propanol, has the -ol ending to indicate highest priority even though the amino group is on the 1 carbon.

Question 16

What is the rate law for the reaction of 1-propanol with HBr in an aqueous environment?

Answer 16

Rate = k_obs [C₃H₇OH] [HBr]

This is the rate of an S_N2 reaction, as this reaction will be.

Question 18

What is the product of the reaction of tert-butanol with HBr in an aqueous environment?

Answer 18

The product is 2-bromo-tert-butane.

This reaction occurs via an S_N1 mechanism, due to the tertiary nature of the carbon that the leaving group is bound to.

Question 32

What is an acid chloride?

Answer 32

An acid chloride is a carboxylic acid derivative, where the -OH has been replaced by a -Cl.

All acid chlorides are named by removing the -oic acid from the end of the name of the parent carboxylic acid and replacing it with -oyl chloride. The three carbon chain below is called propanoyl chloride.

Question 50

How many protons are present on the adjacent carbon to the proton represented by the blue peak (far right) in the NMR spectrum below?

Answer 50

The adjacent carbon has one proton bound to it.

Since the peak is split into a double (2), the (n+1) rule states that 2 = n + 1, so n = 1 proton, hence the adjacent carbon has one proton bound to it.

The spectrum shown is of propene.

Question 56

How can diastereomers be separated?

Answer 56

Since diastereomers differ in their physical shape, they can have different physical properties, a fact which can be used to separate them.

Examples of physical properties which can be used in this way are melting point, boiling point, and solubility.

Question 60

How is a single chiral carbon designated as the R or S form?

Answer 60

To identify a chiral carbon as R or S, follow this procedure:

1. Number all 4 substituents from 1 to 4, with the highest atomic number substituent taking #1, the second highest #2, and so on.
2. Rotate the molecule so that the lowest priority group, #4, is in back.
3. Draw an arrow from 1 to 2 to 3.
4. If the arrow points clockwise, the carbon is the R form. If counterclockwise, the carbon is S.