Problems 621
- Purine is a heterocyclic compound with four nitrogen atoms.
a. Which nitrogen is most apt to be protonated?
b. Which nitrogen is least apt to be protonated?
- Give the product of each of the following reactions:
- Propose a mechanism for each of the following reactions:
- Show two ways that the following compound could be synthesized:
- In a reaction called the Birch reduction, benzene can be partially reduced to 1,4-cyclohexadiene by an alkali metal (Na, Li, or K) in
liquid ammonia and a low-molecular-weight alcohol. Propose a mechanism for this reaction. (Hint:See Section 6.8.)
- The principle of least motion,which states that the reaction that involves the least change in atomic positions or electronic
configuration (all else being equal) is favored, has been suggested to explain why the Birch reduction forms only 1,4-hexadiene.
How does this account for the observation that no 1,3-cyclohexadiene is obtained from a Birch reduction?
- Investigation has shown that cyclobutadiene is actually a rectangular molecule rather than a square molecule. In addition, it has
been established that there are two different 1,2-dideuterio-1,3-cyclobutadienes. Explain the reason for these unexpected
observations.
cyclobutadiene
1,4-cyclohexadiene
Na
NH 3 , CH 3 CH 2 OH
C
O
CH 3
CH CH 2
H+
CH 3
b.
CH 2 CH 2 CHCH CH 2
CH 3
H+
H CH^2 CH^3
3 C
a.
CH 3 CHCH 2 CH 2 CHCH 3
Cl Cl
+
b. AlCl
3
∆
a. CH 2 CH 2 CH 2 CH 2 Cl
AlCl 3
∆
purine
H
N N
N N
