Lecture 7

Question 1

In the free radical mechanism how are bonds broken?

Answer 1

By Homoylsis.

Question 2

What is homolysis?

Answer 2

Breaking of bonds into 2 equal parts.

Question 3

Homoylsis is common in what type of bonds?

Answer 3

Non polar bonds.

No charge on atoms.

Question 4

What is needed for a free radical mechanism?

Answer 4

U/V light- ENERGY

Question 5

What happens in the initiation step in a free radical mechanism?

Answer 5

Radicals are produced.

Question 6

What happens in the propagation step in a free radical mechanism?

Answer 6

Radials react with substrate- New radicals are produced so the reactions continues.

Question 7

What happens in the termination step in a free radical mechanism?

Answer 7

Two radicals combine.

Question 8

What happens in bond formation between radicals?

Answer 8

Each atom DONATES one electron to form a two- electron bond.

Question 9

In fatty acid and prostaglandin biosynthesis what is needed to start the reaction?
What is produced? How?

Answer 9

Enzyme.

Radical is produced as hydrogen is removed.

Question 10

Damage to DNA can cause CANCER. Small amounts of H2O2 in metabolism produce what radicals? Why?

Answer 10

OH radicals because of the weak O2 bond.

Question 11

What substance prevent radicals from completing a harmful reaction? How?

Answer 11

Antioxidants.

Radical reacts with the antioxidant to form a stable radical so they don’t react with a biological molecule.

Question 12

What enzyme has been developed to make use of reactivity of radicals?

Answer 12

CP450

Question 13

In polar/ ionic mechanisms how are bonds broken?

Answer 13

Heteroylsis

Question 14

In polar/ ionic mechanisms which atom to the electrons move to?

Answer 14

The most electronegative atom.

Question 15

What is heterolysis?

Answer 15

One species takes both electrons.

Question 16

What is an electrophile?

Answer 16

Electron lover/ Vacant Orbitals

Fully positive/ slightly positive.

Question 17

What is a nucleophile?

Answer 17

Nucleus lover (Positive)
Lewis bases or lone pair of electrons.

Question 18

Are carbocations electrophiles/ nucleophiles? Why?

Answer 18

Electrophiles

Carbon centre is electron deficient.

Question 19

Are carbanions electrophiles/ nucleophiles? Why?

Answer 19

Nucleophiles

Contain an electron- rich carbon centre.

Question 20

How is the movement of electrons show?

Where does it start from?

Answer 20

Curly arrow

Starts with electrons to wherever they are going.

Question 21

What is an addition reaction?

What happens to pie bond in these reactions?

Answer 21

Reaction where a SMALL molecule is ADDED to the starting material.

Broken.

Question 22

What is an elimination reaction?

What happens to pie bond in these reactions?

Answer 22

Involves REMOVAL of atoms/ groups from 2 ADJACENT atoms in the substrate molecule.

Formed.

Question 23

What is an oxidation reaction?

Answer 23

REMOVAL of H2 or INTRODUCTION of OXYGEN

Question 24

What is an reduction reaction?

Answer 24

ADDITION of H2.

Question 25

What is a condensation reaction?

Answer 25

Reaction involves COMBINATION of two molecules with ELIMINATION of a second small molecule. Addition- Elimination Reaction.

Question 26

What is a substitution reaction?

Answer 26

An atom or group directly attached to a carbon in the substrate molecule is REPLACED by another atom or group.

Question 27

What is a rearrangement reaction?

Answer 27

Molecule undergoes REORGANISATION of bonds to yield an isomeric product.