Unit 2 - Organic Chemistry

Question 1

What is a mechanism?

Answer 1

A mechanism shows the movement of electrons in a chemical reaction.

Question 2

What does nucleophilic substitution produce?

Answer 2

Alcohols from haloalkanes, or amines from haloalkanes.

Question 3

Give 2 examples of sources of hydroxide ions.

Answer 3

KOH and NaOH.

Question 4

Give a source of CN (cyanide).

Answer 4

Potassium Cyanide.

Question 5

Why is hydrogen cyanide (HCN) not a good source of cyanide.

Answer 5

It is extremely dangerous so it is far safer to use other sources.

Question 6

What does elimination produce?

Answer 6

Alkenes from simple haloalkanes.

Question 7

What are the conditions for elimination?

Answer 7

Heated under reflux.

Question 8

How do we test between ketones and aldehydes?

Answer 8

Fehling’s solution: Ketone: No change to the blue solution (due to Fehling’s being a weak oxidising agent, hence no change with a ketone); Aldehyde: Brick-red precipitate of copper (I) oxide.

Question 9

How do we distinguish between a tertiary and a primary/secondary alcohol?

Answer 9

Acidified Potassium Dichromate: Primary/Secondary: Orange to green; Tertairy: No visible change, solution remains orange.

Question 10

What is the functional group of a carboxylic acid?

Answer 10

-COOH (with a double bond between the carbon and one of the oxygens).

Question 11

Give the functional group of an aldehyde.

Answer 11

=O at the END of a carbon chain.

Question 12

Give the functional group of a ketone.

Answer 12

=O somewhere in the middle of a carbon chain.

Question 13

What do we call a C=O?

Answer 13

A carbonyl group.

Question 14

What sort of alcohols can be oxidised under the conditions that we have?

Answer 14

Primary and secondary alcohols.

Question 15

How do we acidify potassium dichromate?

Answer 15

We use concentrated sulphuric acid.

Question 16

How do we test if we have an alcohol in a solution?

Answer 16

If an alcohol is present, it will react with phosphorus (V) chloride to produce a burst of steamy acidic HCl fumes.

Question 17

How do we differentiate between an aldehyde and a ketone?

Answer 17

Fehling’s Solution or Tollen’s Reagent. With Fehling’s: Aldehyde: From blue solution, produces dark red precipitate of copper (I) oxide; Ketone: No visible change (blue solution remains blue). With Tollen’s: Aldehyde: Grey precipitate of silver forms in test tube (silver mirror); Ketone: No change in the colourless solution.

Question 18

What is the functional group of an aldehyde, and how is one produced?

Answer 18

A C=O (and H) at the end of the carbon chain (remember like A is at the start of the alphabet, so the functional group of an Aldehyde is at the start (or end) of a chain).

An aldehyde is produced by partial oxidation of a primary alcohol using acidified potassium dichromate:

CH₃CH₂OH + [O] → CH₃CH=O + H₂O

(Note the O is double bonded to the C, not the H)

To prevent the aldehyde fully oxidising to make a carboxylic acid, we distil off the aldehyde as soon as it forms.

Question 19

What is the functional group of a ketone and how is one produced?

Answer 19

A ketone has a C=O somewhere in the middle of a carbon chain.

They are made by an oxidation by acidified potassium dichromate of a secondary alcohol to form a ketone and water:

CH₃CHOHCH₃ + [O] → CH₃COCH₃ + H₂O