Exam Advanced Organic Chemistry and Laboratory PDF

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The exam paper for Advanced Organic Chemistry and Laboratory...

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CH3CHA UNIVERSITY OF WARWICK FINAL YEAR EXAMINATIONS: March 2018 CHEMISTRY (B.Sc. Year 3, M.Chem Year 4) PAPER I: ADVANCED ORGANIC CHEMISTRY and BIOORGANIC CHEMISTRY Time allowed for candidates offering ONE SECTION: Time allowed for candidates offering TWO SECTIONS:

1½ hours 3 hours

SECTION A:

ADVANCED ORGANIC CHEMISTRY (CH3E9) Answer Question 1 and EITHER Question 2 OR Question 3

SECTION B:

BIOORGANIC CHEMISTRY (CH3F5) Answer ONLY TWO questions from Questions 4, 5 and 6

Percentages in square brackets are intended as a guide to the time candidates should spend in answering the corresponding part of the question. Answers to each section should be written in a separate booklet.

1

CH3CHA

SECTION A: ADVANCED ORGANIC CHEMISTRY (CH3E9) Answer Question 1 and EITHER Question 2 OR Question 3

1. Answer ALL PARTS: (a) Using frontier molecular orbital theory, explain why a thermal suprafacial [4+2] cycloaddition is observed but a thermal suprafacial [4+4] cycloaddition is not. [25%] (b) Complex 1 catalyses the following reaction:

O Ph2P

N Ir 1 H

20 bar H2

(i)

Draw the stereoisomer of the product which will be formed by the reduction of each of the molecules shown below with catalyst 1

Me Ph

CO2Et

MeO

Me

O (ii)

Briefly explain why catalyst 1 is capable of the reduction of double bonds without a neighbouring directing group, whereas Rh and Ru complexes are not able to do this.

[25%]

question 1 continues over the page

2

CH3CHA (c) Answer the following (i)

Draw 3D representations for the two possible structures of the carbene CH2 and state the ground state configuration for each.

(ii)

Draw a mechanism for the reaction of 2 with diiodomethane and Zn/Cu to give 3 and comment on the stereochemical outcome. OH

H

Zn/Cu CH2I2

OH

H

H

2

MeO

H 3

MeO

[25%] (d) Explain the stereochemical outcomes of the following reactions. O

HO H

H OH NaBH4

CH3

Ph

CH3

Ph

then H2O

H OH

CH3

+ Ph

H OH

H OH 83 : 17

O CH3

Ph

Zn(BH4)2

H OH

then H2O

HO H

H OH CH3

Ph

+ Ph

CH3 H OH

H OH 1 : 99

[25%] 2. Answer ALL PARTS: (a) Heating a solution of aryl bromide 4 and Bu3SnH in the presence of the radical initiator, azobisisobutyronitrile (AIBN), produced two products 5 and 6 along with a trace (...