AROMATIC COMPOUNDS/ ALCOHOLS/ ETHERS / THIOLS Flashcards
What is an aromatic compound?
A hydrocarbon that contains one or more benzene-like rings
What is an arene?
a term used to describe aromatic compounds
What is the length of a carbon-carbon single bond and a double bond?
approximately 1.5 bonds each, depicted by alternating double and single bonds
Explain Huckel’s rule
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
What is the difference between ‘arene’ and ‘aryl’ groups
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
How many isomers are possible on a benzene ring with 2 substituents?
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)
How to name a benzene ring with 3 or more substituents?
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’
Explain a halogenation reaction with a benzene ring
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
Explain a nitration reaction with toluene
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
What is a polynuclear aromatic hydrocarbon (PAH)?
a hydrocarbon which contains 2 or more benzene rings. Each pair of rings shares 2 carbon atoms
What is an alcohol?
A compound that has a hydroxyl group (-OH) bonded to a sp3 hybridised C atom, the oxygen atom is also sp3 hybridised
Define diols’ and triols’
Diol: a compound containing 2 hydroxyl groups
Triol: a compound containing 3 hydroxyl groups
What is the difference between a phenol and an alcohol?
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
How do you classify alcohols?
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
List the process for naming alcohols.
- select the longest carbon chain containing the hydroxyl group
- number carbons starting at the end nearer to the hydroxyl group
- number the substituents according to their position in the chain and list them in alphabetical order
- 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
What is an ether?
the functional group of an ether is an oxygen atom bonded to 2 carbon atoms
How do you name ethers?
according to IUPAC
common names are derived by listen 4th alkyl group bonded to oxygen in alphabetical order and adding the word ‘ether’
What is a cyclic ether?
One of the atoms in a ring is oxygen
What are some of the physical properties of ethers?
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
How do ethers react?
Similar to hydrocarbons in their resistance to reactions
What is a thiol?
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
How to name thiols
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
What are the physical properties of thiols?
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
What is the reduction of carbonyl compounds
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
Name 2 common reagents in the reduction of carbonyl compounds
NaBH4 and LiAIH4
What are the products of this reaction:
sodium + ethanol
2Na + 2C2H5OH =>
2C2H5ONa + H2
sodium ethoxide + hydrogen
What happens when you oxidise a primary, secondary and tertiary alcohol?
List some oxidising agents
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
What is a reducing agent and name 2 used in the reduction of carbonyl compounds
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
How is it possible to convert an alcohol into an alkene?
How to determine which isomer occurs from this process?
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
