Topic 10 - Isomerism and aromaticity Flashcards
What is this functional group and it’s defining feature?
Alkene
A double bond.
What is this functional group and what is it defined by?
R-OH
Alcohol
The hydroxyl.
What is this functional group and it’s defining feature?
R-Halogen
Halogeno Alkane
What is this functional group and it’s defining feature?
Aldehyde
Carbonyl group (at end of chain as only one R group)
What is this functional group and it’s defining feature?
Keytone
Carbonyl group
What is this functional group and it’s defining feature?
Acid
Carboxyl group.
What is this functional group and it’s defining feature?
R-NH₂
Amine
amino group (NH₂)
What is this functional group and it’s defining feature?
Amide
Amide group.
What is this functional group?
Acyl (meaning acid) Chloride
What is this functional group?
Acid anhydride (dehydrated acid)
What is this molecule?
Benzene.
What is this benzene molecule and it’s alternative name?
Methyl benzene A.K.A Toluene.
What is this aromatic (benzene) compound?
Chlorobenzene
What is this Benzene compound?
Benzenesulphonic acid
What is this aromatic compound and it’s alternative names?
Phenol
What is this benzene compound?
Nitro benzene.
What is this benzene compound?
1,2-dinitrobenzene.
What is this Aromatic compound?
1,3-Dinitrobenzene
What is this Aromatic Compound?
1,4-Dinitrobenzene
What is This Benzene compound?
Phenyl ammonium Chloride
What is this aromatic compound?
Benzene Carboxylic acid.
What is this Benzene compound?
Ethyl benzene carboxylate
What is this aromatic compound?
Benzene carbonyl chloride
What is this benzene compound?
Benzene Carboxamide
What is this aromatic compound and it’s alternative name?
Benzene carbaldehyde A.K.A Benzaldehyde.
What is this benzene compound?
Phenyl methyl keytone
What is this benzene compound?
Methoxy benzene.
What is a asymmetric Carbon atom.
A carbon atom that has four different atoms or groups attached to it.
What property of asymmetric carbon atoms makes them different to other carbn based molecules.
There are two ways of arranging the four atoms or groups around the central carbon atom and the two ways are mirror images of each-other. They are optical isomers A.K.A enantiomers
What is the asymmetric carbon atom also known as?
A chiral atom
What differences in physical properties do optical isomers have?
None.
What differences do enantiomers have in chemical properties?
They behave in the same way with A-Chiral reagents but may differ in their in their behavior with bio-chemicals e.g enzymes.
How can optical isomers be recognised?
They rotate the plane of polarization of plane polarized light
Outline the properties and give the name of an equi-molar mixture of two enantiomers
An equi-molar mixture of two enantiomers will be optically inactive (will not rotate the plane of polarisation of plane polarised light) and is called a racemic mixture or racimate.
What is the molecular formula of benzene and what might this lead us to expect and how does it defy our expectations?
C₆H₆
With this formula it would be expected to be very unsaturated with several double bonds and so to be reactive by addition
What structure was suggested for benzene and by whom?
Kekulè suggested a structure which involved a ring of Carbon atoms with alternating single and double bonds
How are the bonds in Benzene formed?
The bonding is believed to be two sp2 hybrid orbitals with two carbon atoms and one hydrogen atom in a planar ring. The remaining C electron forms π bonds becoming delocalized as a cloud of electrons above and below the plane of the ring. Each Carbon atom uses a 2s orbital and two of the three 2p orbitals to form the three sp2 Hybrid orbitals
What is a sigma bond?
Sigma bonds form when orbitals overlap end ways.
Sigma bonds are stronger than π bonds because they have more overlap.
What is a π bond?
A π bond forms when orbitals overlap sideways.
What evidence is there for this structure of Benzene?
How can nitration of benzene to produce nitrobenzene be achieved?
This is an electrophillic substitution reaction whereby the nitronium ion (NO₂⁺) replaces a hydrogen atom on the benzene ring as it is attracted by the high concentration of electrons. The nitronium ion is created in site by reacting conc H₂SO₄ and conc nitric acid.
****(Mechanism needed, consult notes)****
What happens in the nitration of benzene if the temprature rises above 55°C?
Dinitrobenzene benzene is produced.
Compare the stability of benzene to Alkanes and give a reason for your answer.
Benzene is more stable and less reactive than alkenes because of the delocalization of electrons.
How could you distinguish Benzene from an Alkene?
Benzene will undergo some addition reactions (chlorine, hydrogen) but will not decolourise bromine water or react with potassium ManganateVII as an Alkene like ethene would. Ethene only reacts by addition whereas benzene undergoes substitution reactions.
Compare the alkaline hydrolysis (warming with KOH or NaOH) of chlorobenzene and chlorobutane and give an explaination.
Chlorobutane is much more reactive than chlorobenzene so with chlorobenzene hydrolysis takes much longer. The electrons of the Chlorine atom not used in bonding becomes part of the delocalized rings of electrons above and below the plane of the benzene ring. This makes the molecule very stable and resistant to attack by nucleophiles.
What halogens will react with benzene and what conditions are necessary?
This is another example of electrophillic substitution. Chlorine or bromine (not iodine) react to form chlorobenzene or bromobenzene with a catylist called a halogen carrier. Aluminum chloride or iron-III-chloride or the equivalent bromine compounds are examples.
****(Mechanism needed)****
What is a friedel-crafts alkylation?
An alkyl group can be substituted into a benzene ring using a halogeno Alkane in the presence of a friedel-Crafts catylist ie aluminium-chloride, iron-III-Bromide etc warmed under reflux
C₆H₆ + C₂H₅Cl → C₆H₅C₂H₅ + HCl
