AROMATIC COMPOUNDS/ ALCOHOLS/ ETHERS / THIOLS

Question 1

What is an aromatic compound?

Answer 1

A hydrocarbon that contains one or more benzene-like rings

Question 2

What is an arene?

Answer 2

a term used to describe aromatic compounds

Question 3

What is the length of a carbon-carbon single bond and a double bond?

Answer 3

approximately 1.5 bonds each, depicted by alternating double and single bonds

Question 4

Explain Huckel’s rule

Answer 4

4n+2 rule: in order to be aromatic, a molecule must have a certain number of pi electrons (electrons with pi bonds, or lone pairs with p orbitals) within a closed loop of parallel, adjacent p orbitals

Question 5

What is the difference between ‘arene’ and ‘aryl’ groups

Answer 5

arene is any monocyclic or polycyclic aromatic hydrocarbon while aryl is any univalent organic radical derived from an aromatic hydrocarbon by removing a hydrogen atom

Question 6

How many isomers are possible on a benzene ring with 2 substituents?

Answer 6

3 isomers, they may be located by numbering the atoms of the ring or using the locators ortho (o, substituents 1 C atom away), meta (m, substituents 2 C atoms away), and para (p, substituents 3 C atoms away)

Question 7

How to name a benzene ring with 3 or more substituents?

Answer 7

If one of the substituents imparts a special name, name the molecule as a derivative of that parent

If none of the substituents imparts a special name, number the substituents to give the smallest set of numbers, and list them in alphabetical order before the ending ‘benzene’

Question 8

Explain a halogenation reaction with a benzene ring

Answer 8

For the reaction with benzene to be possible, an activated halogen such as AlCl4 is added to induce electrophilic activity and cause a transfer of electrons to take place

Question 9

Explain a nitration reaction with toluene

Answer 9

The treatment of toluene with nitric acid in the presence of sulfuric acid results in 2,4,6-trinitrotoluene under carefully controlled condition and several processes

Question 10

What is a polynuclear aromatic hydrocarbon (PAH)?

Answer 10

a hydrocarbon which contains 2 or more benzene rings. Each pair of rings shares 2 carbon atoms

Question 11

What is an alcohol?

Answer 11

A compound that has a hydroxyl group (-OH) bonded to a sp3 hybridised C atom, the oxygen atom is also sp3 hybridised

Question 12

Define diols’ and triols’

Answer 12

Diol: a compound containing 2 hydroxyl groups

Triol: a compound containing 3 hydroxyl groups

Question 13

What is the difference between a phenol and an alcohol?

Answer 13

The functional group of a phenol is a hydroxyl group bonded to a benzene ring

Name substituted phenols either as derivatives of phenol; or by common names

Question 14

How do you classify alcohols?

Answer 14

As primary, secondary or tertiary

Primary: a hydroxyl group attached to a carbon atom with 1 substituent attached

Secondary: a hydroxyl group attached to a carbon atom with 2 substituents attached

Tertiary: a hydroxyl group attached to a carbon atom with 3 substituents attached

Question 15

List the process for naming alcohols.

Answer 15

1. select the longest carbon chain containing the hydroxyl group
2. number carbons starting at the end nearer to the hydroxyl group
3. number the substituents according to their position in the chain and list them in alphabetical order
4. some well known alcohols have common names: to derive common names, we have the alkyl group bonded to the -OH group and add the word alcohol, compounds contains 2 and 3 -OH groups are named as diols and trials respectively

Question 16

What is an ether?

Answer 16

the functional group of an ether is an oxygen atom bonded to 2 carbon atoms

Question 17

How do you name ethers?

Answer 17

according to IUPAC

common names are derived by listen 4th alkyl group bonded to oxygen in alphabetical order and adding the word ‘ether’

Question 18

What is a cyclic ether?

Answer 18

One of the atoms in a ring is oxygen

Question 19

What are some of the physical properties of ethers?

Answer 19

Polar molecules, O bears a partial negative charge

Only weak forces of attraction exist between ether molecules in the pure liquid

Boiling points of ethers are close to those of hydrocarbons of similar weight

Ethers have lower boiling points than alcohols of the same molecular formula

Question 20

How do ethers react?

Answer 20

Similar to hydrocarbons in their resistance to reactions

Question 21

What is a thiol?

Answer 21

compound containing an -SH (sulfhydryl group)

Thiols are added as the odourants in natural gas, and are responsible for smells such as those from rotten eggs and sewage

Question 22

How to name thiols

Answer 22

IUPAC names are derived in the same manner as are the names of alcohols

To show that the compound is a thiol, add -thiol to the parent alkane

Question 23

What are the physical properties of thiols?

Answer 23

Non-polar covalent S-H bonds due to small electronegativity difference between sulfur and hydrogen

Mostly dispersion forces between molecules and rarely engage in any H bonding

Lower boiling points and less soluble in water than alcohols of similar molecular weight

Question 24

What is the reduction of carbonyl compounds

Answer 24

The formal addition of H2 to carbonyl C=O double bond

Aldehydes (1 C & 1 H attached to carbonyl carbon) are reduced to secondary alcohols

Ketones (2 alkyl or aryl groups attached to carbonyl carbon) are reduced to secondary alcohols

Carboxylic acids (OH attached to carbonyl carbon) and esters can be reduced to form primary alcohols

Question 25

Name 2 common reagents in the reduction of carbonyl compounds

Answer 25

NaBH4 and LiAIH4

Question 26

What are the products of this reaction:
sodium + ethanol
2Na + 2C2H5OH =>

Answer 26

2C2H5ONa + H2

sodium ethoxide + hydrogen

Question 27

What happens when you oxidise a primary, secondary and tertiary alcohol?

List some oxidising agents

Answer 27

Primary: You get an aldehyde or a carboxylic acid
Secondary: you get a ketone
Tertiary: resistant to oxidisation

Oxidising agents: potassium permanganate, bleach, nitric acids

Question 28

What is a reducing agent and name 2 used in the reduction of carbonyl compounds

Answer 28

A compound that readily loses electrons to another during a reaction

2 common reagents used for the reduction of carbonyl compounds are: NaBH4 and LiAlH4

Question 29

How is it possible to convert an alcohol into an alkene?

How to determine which isomer occurs from this process?

Answer 29

Through acid-catalysed dehydration, by using an acid catalyst such as H2SO4 you can remove the H and OH
group

When isomeric alkenes occur through this process, the alkene having the greater number of alkyl groups on the double bond generally predominates