Problems 335
- The experiment shown below and discussed in Section 8.8, showed that the proximity of the chloride ion to C-2 in the transition
state caused the 1,2-addition product to be formed faster than the 1,4-addition product:
a. Why was it important for the investigators to know that the reaction was being carried out under kinetic control?
b. How could the investigators determine that the reaction was being carried out under kinetic control?
- A student wanted to know whether the greater proximity of the nucleophile to the C-2 carbon in the transition state was what
caused the 1,2-addition product to be formed faster when 1,3-butadiene reacts with HCl. Therefore, he decided to investigate the
reaction of 2-methyl-1,3-cyclohexadiene with HCl. His friend, Noel Noall, told him that he should use 1-methyl-1,3-cyclohexa-
diene instead. Should he follow his friend’s advice?
- a. Methyl orange (whose structure is given in Section 8.12) is an acid–base indicator. In solutions of it is red, and in
solutions of it is yellow. Account for the change in color.
b. Phenolphthalein is also an indicator, but it exhibits a much more dramatic color change. In solutions of it is
colorless, and in solutions of it is deep red-purple. Account for the change in color.
phenolphthalein
OH
O
O
OH
pH 7 8.5,
pH 6 8.5,
pH 7 4,
pH 6 4,
CH 2 CHCH CHCH 3 + DCl CH 2 CHCH CHCH 3 CH 2 CH CHCHCH 3
D Cl D Cl
+
− 78 °C
3-D Molecule:
Phenolphthalein
