These are the reaction steps in a certain polymerization process, which may occur by either an uncat — Kinetics / Organic Chemistry Chemistry Question
Problem Context
These are the reaction steps in a certain polymerization process, which may occur by either an uncatalyzed or an acid-catalyzed pathway.
Write a balanced equation for the overall reaction.
Model Answer
RCOOH + R’OH → RCOOR’ + H2O
Name the functional groups labeled [1], [2], and [3].
Model Answer
Functional group I – carboxyl group (acid)
Functional group II – hydroxyl group (alcohol)
Functional group III – ester
Given these data for the acid-catalyzed reaction, find the rate law and the value of k, specifying its units.
Model Answer
RCOOH is first order.
R’OH is first order.
Trials 1 and 4 can be used to determine the order with respect to HA. [RCOOH] is held constant; however, both [R’OH] and [HA] vary. The effect of [R’OH] is:
1.43 and then (1.43)(4.60) = 6.57 M/min
The effect of [HA] is 1.50. HA is first order.
Rate = k[RCOOH] [R’OH] [HA]
k = 75 M–2 ·min–1
Identify the rate-determining step based on the rate law found in question 3c. Explain your answer.
Model Answer
Rate determining step could be either:
Step 2 that involves R’OH and product from the reaction of RCOOH and HA, or
Step 3 that involves the breakup of product in step 2.
The initial reaction rate can be followed spectrophotometrically by quenching the reaction and determining the amount of ROH left by its reaction with dichromate ion, Cr2O7 2–.
i. Write a balanced equation for the reaction of Cr2O7 2– with R´OH in acid solution. Assume Ŕ is CH3CH2– and the products of the reaction are Cr3+ and CH3COOH.
Model Answer
2Cr2O7 2– + 3CH3CH2OH + 16H+ → 4Cr3+ + 3CH3COOH + 11H2O
ii. Describe the color change expected for the reaction written in question 3e, part i.
Model Answer
The color will change from orange (Cr2O7 2–(aq)) to green (Cr3+(aq)).