Organic Chemistry: Synthesis and Reactions Assignment 6

This document provides comprehensive solutions to a chemistry assignment focusing on organic chemistry. The assignment covers a range of topics, including the prediction of products from reactions involving halogenation, substitution reactions (SN2 and SN1), and the application of reaction mechanisms. The solutions include detailed explanations, step-by-step mechanisms using curved arrows, identification of nucleophiles and leaving groups, and predictions of product stereochemistry. The document also addresses reaction kinetics, the effects of solvents and concentrations on reaction rates, and the synthesis of various organic compounds. Furthermore, the assignment explores the concepts of regioselectivity and stereoselectivity in organic reactions. The solutions are designed to aid in understanding and mastering the fundamental principles of organic chemistry.

Assignment 6
Marks for Assignment 6 total 80 (10 marks for each question).
1. Answer the following questions:
a. Draw the monofluorinated products formed in the greatest amount and the
least amount when 1-methyl-1-(methylethyl)-cyclohexane is exposed to F2
and UV light.
b. Draw the complete mechanism for the formation of the major product
above using single-barbed arrows to show the movement of a single electron.
Label all the steps (chain-initiating and others).
c. Are there any products possible that have no fluorine atoms present?
Explain.

2. For each pair of molecules, answer the question listed for SN2 reactions :
a. Identify the leaving groups present in each molecule below. Which is a better
leaving group and why?

b. Identify the most nucleophilic atom present in each molecule below. Which
molecule is a better nucleophile and why?
CH3-CH2-O-Na CH3-S-K
c. Identify which reaction below would give the faster SN2 reaction and explain
why.
a)
Between OH- and Cl-, Cl- is better leaving group because electron on Cl will be more
stable due to bigget size of Cl.. Due to bigger size elctron density will be moew and
hence potential energy will be less for Cl-
Answer: Cl-
2nd answer: I- (Due to bigger size
b.)
In 1st one nucleophilic atom is: CH3-CH2O-
In 2nd one: CH3-S-
CH3-S- is more nucleophilic.
Here negative charge is on O and S. According to fajan's rule: Bigger anion will form
covalent bond more rapidly than smaller anion.
c)
In protic solvent: nucleophilic strength is: I- > Br-
InA protic solvent: nucleophilic strength is: I-< Br-
Recation will be faster in protoc solvent.
Hence down reaction will be faster
3. The reaction below has been found to follow second-order kinetics.
a. Predict the rate of reaction for Experiment #2 and Experiment #3 in the
following table of experimental data.

Expt #
[CH3Br]] in
mol•L–1 [NaSCN] in
mol•L–1
Rate in
mol•L–1•s–1
1 0.15 0.15 3.0  10–8
2 0.15 0.45
3 0.30 0.15
b. Clearly draw the mechanism for this reaction using curved arrows to show
the movement of a pair of electrons. Identify the nucleophile and the leaving
group.
c. What would you expect to happen to the rate of reaction if methanol was
used as the solvent instead of acetone?
a) in experiment 2 concentration of NaSCN increased 3 times so rate also will increase
three times. so 9.0 x 10-8
in experiment 3 CH3Br doubled concentration also doubled so rate also doubled 6.0 x
10-8
4. Answer the following questions for the reaction below:

+ HBr
a. Draw out the structures for the two substitution products possible from the
above reaction.
b. Explain why there are two products possible by drawing out the mechanism
for this reaction using curved arrows to show the movement of electron pairs.
Identify the leaving group and the nucleophile.
c. Would you expect the two products A and B to be formed in the same
amounts or would one be formed in greater amounts? Explain.
d. Describe what effect (if any) that doubling the concentration of the
nucleophile in this reaction would have on the reaction rate.

5. Secondary alkyl halides can undergo substitution by different mechanisms,
depending on the reaction conditions. Suggest suitable reaction conditions for a)
and b), including nucleophiles and solvents, and draw the stereochemistry of the
products.
3. Clearly and neatly draw the monobromination products from the radical
halogenation of the molecule at the carbons indicated below (be sure to indicate
correct stereochemistry). Answer the questions posed.
a. Draw the 2 products from a monobromination at a, and briefly explain which
you would expect to be formed in the greatest amount.

b. Draw the 2 products from a monobromination at b, and briefly explain which
you would expect to be formed in the greatest amount.
c. Draw the product from a monobromination at c, and briefly explain why
only one product is formed.

6. Predict the major organic product(s) for each of the following reactions. If there is
no reaction, briefly explain why.

7. Explain by means of reaction equations how you would synthesize each of the
following compounds. Show reaction conditions, reagents, and solvents in your
equations.