29 - INTRODUCTION TO ORGANIC CHEM

Question 1

What is a functional group?

Answer 1

• atom/ group of atoms that determines its chemical characteristics and physical properties

Question 2

Name and state the functional group: CH3COCl

Answer 2

• ethanoyl chloride (acyl chloride)

Question 3

Name and state the functional group: CH3CH2NH2

Answer 3

• ethanamine (amine)

Question 4

Name and state the functional group: CH3CH2CONH2

Answer 4

• propanamide (amide)

Question 5

Name: C6H5(CH2CH2CH3)

Answer 5

• propylbenzene (alkyl group –> propyl)

Question 6

Draw out: 2,3- dimethylphenol

Answer 6

(check google)

Question 7

Explain and describe the structure of benzene

Answer 7

• each C is sp2 hybridised
• and forms 3 alpha bond pairs
• unhybridised p-orbitals overlap side by side forming pi bond
• electrons are delocalised and spread over the ring
• shape: planar, flat with 120 bond angle
• bond length of C-C and C=C is similar/ identical

Question 8

State the two types of stereoisomerism

Answer 8

• optical isomerism –> forms 2 enantiomers (tetrahedral with chiral centre)
• geometrical isomerism –> cis/trans isomers (planar)

Question 9

State the definition of stereoisomerism

Answer 9

• molecules that have the same structural formula but atoms are arranged differently in space

Question 10

Explain what are enantiomers

Answer 10

• formed by optical isomerism
• they are non-superimposable mirror images of each other
• physical and chemical properties are identical except:
  > ability to rotate plane polarised light
  > biological activity

Question 11

What does it mean when a solution is optically active?

Answer 11

• when there is an uneven mixture of enantiomers
• there is a net effect for plane polarised light to be rotated
• hence, it is optically active

Question 12

What is a racemic mixture?

Answer 12

• there are equal amounts of each enantiomer
• no net effect for plane polarised to be rotated
• therefore it is optically inactive

Question 13

Why do enantiomers have different biological activity?

Answer 13

• chiral enzyme and substrate has complementary/ exact shape with each other to bind
• mirror image of the enzyme will not have the exact shape and unable to bind to the active site of the substrate

Question 14

What is the use of chiral catalyst?

Answer 14

• to produce pure, single enantiomer

Question 15

Why is it important to separate to produce a pure, single enantiomer?

Answer 15

> each enantiomer have opposite biological activities

> therefore they are separated to reduce side-effects & decrease dosage (pure –> more potent)