Organic chem II

Question 1

2-bromobutane and cyanide ions react together by Sn2 mechanism- Draw the structure of the transition state formed in this reaction

Answer 1

check 17.1.3 question 1
answers online
(edexcel alevel book 2 )

Question 2

What is the functional group for an aldehyde

Answer 2

RCOH (hydrogen attached to carbonyl group)

Question 3

How do we name aldehydes

Answer 3

• Count carbon chain
• Name molecule as if its an alkane
• Add “-al” to the end of it

Question 4

With aldehydes how do we know which is carbon 1

Answer 4

Carbon 1 is always the carbon with the carbonyl group attached to it

Question 5

What is the functional group for a ketone

Answer 5

RCOR (carbonyl group with 2 different groups also attached to it

Question 6

How do we name ketones

Answer 6

• Count carbon chain
• Name molecule as if its an alkane
• Add “-one” to the end of it

Question 7

Do ketones or aldehydes require locants? give reason for answers

Answer 7

Ketone - yes - as it can be placed anywhere in carbon chain

Aldehyde - rarely - as it tends to be placed on ends of molecules

Question 8

What are the 2 carbonyl compounds

Answer 8

Ketones

Aldehydes

Question 9

Why can’t carbonyl groups undergo hydrogen bonding?

Answer 9

As they don’t have a polar OH bond so they can’t form hydrogen bonds with other ketones or aldehydes

Question 10

what kind of attack are carbonyl groups more susceptible too? and why?

Answer 10

Nucleophilic attack due to C=O polar bond nature (delta positive C, delta negative O)

Question 11

State a few physical properties of Aldehydes

Answer 11

Small chain aldehydes = Unpleasant smells

Large chain aldehydes = Pleasant smells used in parfumes

Question 12

which of these have the highest-lowest boiling point, and explain why?
alkane,alcohol,ketone&aldehyde

Answer 12

Highest - Lowest
alcohol, ketone&aldehyde, alkane

Alcohol - contain OH bond (as well as london and dipole interactions)so can undergo hydrogen bonding with other substances

Ketones&Aldehyde - london forces and dipole interaction - no hydrogen bonding with itself

Alkanes - weak intermolecular forces -London forces

Question 13

Why is propanone soluble in water

Answer 13

Short chain ketone

Can form hydrogen bonds with water

Question 14

what makes the carbon double bond in carbonyls polar

Answer 14

Oxygen is far more electronegative than carbon so has a strong tendency to pull electrons in a carbon-oxygen bond towards itself.
One of the two pairs of electrons in carbon-oxygen double bond is even more easily pulled towards the oxygen.

Question 15

what are nucleophiles

Answer 15

Negative ion or negatively charged part of a molecule that donates lone pairs of electron to electron deficient atoms

Question 16

why aren’t long chain aldehydes or ketones soluble in water

Answer 16

As chain lengths increase, the hydrogen bonding is interrupted by the rest of the hydrocarbon getting in
between water molecules,breaking the relatively strong hydrogen bonds between water molecules

Question 17

how do ketones and aldehydes differ?

Answer 17

Aldehydes have a hydrogen attached to C=O bond which makes them more easily oxidised
ketones don’t have a hydrogen attached to C=O bond and so require strong oxidising agents

Question 18

What state are majority of carbonyl groups at room temp

Answer 18

liquids due to relatively low melting and boiling points

Question 19

Why does the boiling/melting point of carbonyl groups increase as the chain length increases

Answer 19

Larger the molecule= more london forces and therefore temporary dipole interactions