Unit 4.1 - Stereoisomerism + start of 4.2 Flashcards
Organic chemistry
The chemistry of carbon compounds, looking into the chemistry of different homologous groups
Homologous series
Groups of related compounds with the same functional group
What do members of a homologous series have in common?
The same functional group
The same general formula
Similar chemical properties
Gradually changing physical properties
Functional group
An element or group of elements that is responsible for the chemical properties of the compound (i.e - it provides a reactive site)
Alkane systematic name
-ane
Alkene systematic name
-ene
Halogenoalkane systematic name
chloro, bromo, iodophor
Primary alcohol functional group + systematic name
CH2OH
-1-ol
Secondary alcohol functional group + systematic name
CH(OH)
-2-ol
Aldehyde functional group and systematic name
CHO
-al
Ketone functional group and systematic name
-C=O-C-
-one
Carboxylic acid functional group and systematic name
-C=O-OH
-oic acid
Ester functional group and systematic name
-COOC-
-oate
Acid chloride functional group and systematic name
-COCl
-oyl chloride
Acid anhydride functional group and systematic name
(-CO)2O
-oic anhydride
Amide functional group and systematic name
-CONH2
-amide
Nitrile functional group and systematic name
-CN
-nitrile
Amine functional group and systematic name
-NH2
-amine
Amino acid functional group and systematic name
CN(NH2)COOH
——
Alkanes chemical reactions
Combustion
Cracking - homolytic fission of the C=C bond
Photo chlorination - free radical substitution
Alkenes chemical reactions (include any specific conditions required)
Catalytic hydrogenation (reduction) - nickel catalyst, production of margarine, 150C
Addition of bromine (electrophilic addition with halogen) - RT
Decolorisation of potassium manganate (VII)
Additional of water as steam - conc. H2SO4 or phosphoric acid, 300C, 60atm
Addition of hydrogen bromide - RT (propene = electrophyllic addition)
Addition polymerisation - 2000atm, 250C, O2 initiator
Preparation of alkenes
From halogenoalkanes using elimination reactions
Chemical reactions of halogenoalkanes
Nucleophillic substitution - reflux, distillation, aqueous sodium hydroxide
Elimination -reflux, ethanolic sodium hydroxide
Preparation of halogenoalkanes
Direct chlorination of alkanes - free radical substitution, UV light
Reactions of alcohols
Oxidation
-oxidising agent, acidified potassium dichromate, heated
Primary: alcohol —> aldehyde —> carboxylic acid
(Heat + distill) (reflux)
Secondary: alcohol —> ketone
(Reflux with acidified potassium dichromate)
Dehydration
Conc. H2SO4 in excess
170C
=alkene
Preparation of alcohols
From alkenes - electrophillic addition
H20 (steam)
300C
60atm pressure
Phosphoric acid
By fermentation, then distillation
35C
Zymase enzymes
Absence of air
Chemical reactions of carboxylic acids
Acid + base —> salt + water
Acid + metal —> salt + H2
Acid + carbonate —> salt + CO2 + H2O
Carboxylic acid + alcohol —><— ester + H2O
-conc. H2SO4
-heat + distillation
How is an amide prepared?
Carboxylic acid with ammonia
How is a nitrile prepared?
By dehydrating amides
How is an ester prepared?
Using carboxylic acids with alcohols
How are esters named?
1st part —> alcohol with name changed to end with -yo (carbons after COO group)
2nd part —> carboxylic acid or acid anhydride with name changed to end in -oate (carbons up to and including COO)
Primary alcohols
The carbon which carries the OH- group is only attached to 1 alkyl group (1 other carbon atom)
Secondary alcohols
The carbon which carries the OH- group is attached to 2 alkyl groups (which may be the same or different)
Test for alkenes
Bromine water is decolorised (orange —> colourless)
Potassium manganate (VII) (purple —> colourless)
Test for halogenoalkanes
1.) aqueous sodium hydroxide + heat to hydrolyse it
2.) neutralise the excess NaOH with dilute nitric acid (removes OH- ions that could interfere)
3.) aqueous silver nitrate
Chlorine - white ppt
Bromine - cream ppt
Iodine - yellow ppt
Test for alcohols
Acidified dichromate solution
Primary —> carboxylic acid
Secondary —> ketone
Tertiary —> no reaction
Orange —> green
(The dichromate (VI) ion is reduced to the chromium (III) ion)
Test for carboxylic acids
1.) addition of a metal carbonate/hydrogencarbonte
2.) effervescence forms - test this for CO2 (turns limewater milky)
Limewater
Calcium hydroxide
Compounds having carbon chains
Aliphatic compounds
What are the stages to naming organic compounds?
- The longest carbon chain is found
- The functional group is found
- Any side groups (radials) are found
- Assign a number to each carbon atom in the longest chain to find the position of functional groups or side groups. Do the numbering forwards and backwards and always use the lowest numbers possible.
7 C atom parent alkane
Heptane
Methane radical + formula
Methyl
CH3
Ethane radical and formula
Ethyl, CH3CH2
Propane radical and formula
Propyl, CH3CH2CH2
What are alkenes referred to as being since they C=C bonds?
Unsaturated
What is the feature that gives rise to E-Z isomerism?
C=C bond
Why do single bonds not lead to E-Z isomerism?
They can freely rotate = atoms in the bond are interchangeable
Why do double bonds lead to E-Z isomerism?
No free rotation
Why is there no free rotation in double bonds?
Due to the pi bond
E-Z isomers
Same molecular and structural formula but different spatial arrangement of atoms
E isomers
Atoms with the highest atomic masses on different sides of the double bond
Z isomers
Atoms with the highest atomic masses on the same side of the double bond
what does a COO group imply the presence of?
an ester
can amines be secondary?
yes
Stereo isomers definition
Stereo isomers have the same molecular and structural formulae but differ in the spatial arrangement of their atoms
How can steroisomerism be divided into groups?
- E-Z isomerism
- Optical isomerism
What is divided into E-Z and optical isomerism?
Steroisomerism
Explain what E-Z isomerism is
The absence of free rotation around the C=C bond in alkenes due to the presence of the pi bond can result in two different molecules which are E-Z isomers
Why is there no free rotation around the C=C bond in alkenes?
Due to the presence of the pi bond
What is a pi bond in an alkene caused by?
The sideways overlap of p-orbitals
How do we remember which is which with E-Z isomers?
z isomers —> “zame zide”
How do we work out the priority group with E-Z isomers?
We combine the atomic masses in order to work out the priority group. The priority group will have the biggest atomic masses.
In which situation do we not have E-Z isomerism? What is required to ensure that there is?
If either atoms on both sides are the same then there’s no E-Z isomerism. We need 2 different groups attached to the carbon atoms making the double bond
Name a molecule that exibits optical isomerism
Butan-2-ol
Describe optical isomers
Have the same molecular and structural formulae but differ in the spatial arrangement of the atoms
What do we call the isomers of, for example, butan-2-ol?
Optical isomers
Why is butan-2-ol able to form optical isomers?
It has a chiral centre
What is the thing that allows molecules to form optical isomers?
Having a chiral centre
Chiral centre
A carbon atom which has four different atoms or groups attached to it
A carbon atom which has four different atoms or groups attached to it
Chiral centre
Give examples of chiral objects
Hands and gloves
What type of molecules are the only ones to have optical isomers?
Chiral molecules
Describe the two optical isomers of a molecule
Mirror images of each other
Are non-super imposable on one another
Non-super imposable
Can distinguish them and if you place one on other, one will no longer be visible
Name for a pair of optical isomers
Enantiomers
Enantiomers
Pair of optical isomers
Do optical isomers generally have the same physical properties?
Yes
What is the physical property that optical isomers have that isn’t the same?
Their behaviour towards polarised light
Plane polarised light
Light that only vibrates in a single plane
How can we identify the different optimal isomers of enantiomers?
By analysing their behaviour towards plane polarised light
How do enantiomers effect plane polarised light differently?
Will rotate it in opposite directions
Racemic mixture
An aqueous solution that contains equimolar quantities of the enantiomers
An aqueous solution that contains equimolar quantities of the enantiomers
Racemic mixture
What does a racemic mixture do to plane polarised light and why?
Will not rotate it as the enantiomers will cancel out each other’s rotation
What is light a form of?
Elecromagnetic radiation
What type of waves does light consist of?
Transverse
How is light seen when viewed at right angles to the direction of travel?
Is seen to vibrate in many planes
When is light seen to vibrate in many planes?
When it is viewed at right angles to the direction of travel
When are all vibrations except those in one plane for light removed?
If light is passed through a piece of Polaroid
What happens if light is passed through a piece of Polaroid?
All vibrations except for those in one plane are removed
What type of molecules are able to rotate the plane of polarised light?
Molecules with a chiral centre
What are molecules with a chiral centre able to do?
Rotate the plane of polarised light
What happens when a solution of a molecule containing a chiral centre has plane polarised light passed through it?
The plane of the light will be rotated
Name for one optical light rotating light in a clockwise direction
Dextrorotatory
Dextrorotatory
Rotating light in a clockwise direction
Name for one optical light rotating light in an anti-clockwise direction
Laevorotatory
Laevorotatory
Rotating in an anti-clockwise direction
Right side of an optical isomer
Rectus
Left side of an optical isomer
Sinister
Why is it important to know about optical isomer?
Thalidomide was a drug taken by pregnant women to prevent nausea.
It wasn’t discovered until many had been taking it that some of its optical isomers caused birth defects whilst others didn’t
It resulted in severe birth defects in thousands of children
Why can a racemic mixture be described as an equimolar mixture containing equal amounts of both enantiomers?
Because enantiomers have the same molecular formula and the same Mr. Therefore equal amounts will contain the same number of moles of each enantiomer
Why are aromatic compounds called this?
The name comes from its smell
What do aromatic compounds contain?
A benzene ring
What type of compounds contain benzene rings?
Aromatic compounds
Benzene formula
C6H6
Where does benzene come from?
It’s a natural constituent of crude oil
What are the risks of benzene?
It’s highly toxic and carcinogenic
Aliphatic meaning
Straight chain
What type of compounds that include benzene rings are named in a different way to aliphatic compounds?
Substituted aromatic compounds in which one or more of the hydrogen atoms on the benzene ring have been replaced by other elements or groups
Are the structures of carbon and hydrogen atoms shown in Benzene’s structure? Why?
No, for the sake of brevity
List all of the homologous series of the compounds in which the functional group is considered to be a substudent of the benzene ring
Hydrocarbons
Aromatic halogeno
Carboxylic acid
Nitro
Aliphatic halogeno
Aromatic aldehyde
Aromatic acid chloride
Substuent
An atom or group that replaces another atom or group
How are compounds in which the functional group is considered to be a substuent of the benzene ring named?
By prefixing or suffixing the word benzene with the name of the functional group
Hydrocarbon homologous series (in an aromatic compound) functional group and systematic name
(No functional group)
-benzene
Aromatic halogeno homologous series (in an aromatic compound) functional group and systematic name
-Cl, -Br, -I
-chloro etc
Carboxylic acid homologous series (in an aromatic compound) functional group and systematic name
-COOH
-carboxylic acid
Nitro homologous series (in an aromatic compound) functional group and systematic name
-NO2
-nitro
Aliphatic halogeno homologous series (in an aromatic compound) functional group and systematic name
-Cl, -Br, -I
-chloroalkyl etc
Give an example of an aliphatic halogeno to explain what is is
C6H5CH2Cl
1-chloromethyl-Benzene
Where does the aliphatic carbon go in an aliphatic halogeno?
Between the benzene and the halogen
How would you name this and what is it?
C6H5CHO
Benzene carbaldehyde or benaldehyde
It’s an aromatic aldehyde
What does aromatic basically mean?
Has a benzene ring
How would you name this and what is it?
C6H5COCl
Benzene Carbonyl Chloride / Benzoyl chloride
Name all of the homologous series of the compounds in which the benzene ring, known as the phenyl group (C6H5-) is considered to be a substituent of the other group and the compound is named by prefixing the name of the substituent group with phenyl
Amine
Alkene
Ketone
Aliphatic alcohol
What is the benzene ring also known as?
The phenyl group
The phenyl group formula
C6H5-
What do all of the following have in common?
Amine
Alkene
Ketone
Aliphatic alcohol
They’re homologous series of compounds in which the benzene ring, known as the phenyl group (C6H5-) is considered to be a substituent of the other group and the compound is named by prefixing the name of the substituent group with phenyl
What do all of the following have in common?
Hydrocarbons
Aromatic halogeno
Carboxylic acid
Nitro
Aliphatic halogeno
Aromatic aldehyde
Aromatic acid chloride
They’re the homologous groups of compounds in which the functional group is considered to be a substuent of the benzene ring. The compound is named by prefixing or suffixing the word benzene with the name of the functional group.
Amine homologous series (in aliphatic compounds) functional group and systematic name
-NH2
-amine
Alkene homologous series (in aliphatic compounds) functional group and systematic name
-CH2=CH
-ene
Ketone homologous series (in aliphatic compounds) functional group and systematic name
-C=O-R
-one
Aliphatic alcohol homologous series (in aliphatic compounds) functional group and systematic name
-CH2OH
-ol
Can ethanone exist?
No, but phenylethanone can
Phenylethene alternative name
Styrene
Styrene
Phenylethene
Phenylamine other name
Aniline
Aniline
Phenylamine
Methyl benzene other name
Toluene
Toluene
Methyl benzene
Another word for benzene carboxylic acid
Benzoic acid
Would an ester include benzene or phenyl in its name in an aliphatic compound?
Phenyl
Give the homologous series, functional group and systematic name of compounds in which a trivial (old) name has been retained
Phenol
-OH
-phenol
Another word for phenol
Hydroxybenzene
What is phenol important for?
The synthesis of drugs e.g: paracetamol and aspirin
Which benzene is important for the synthesis of drugs such as paracetamol and aspirin?
Phenol
How do we name an aliphatic compound when there is more than one substituent on the benzene ring?
The ring is numbered so that one group is at position 1 and the other is numbered with reference to this group
When are the numbers 5 and 6 used in the naming of a benzene ring?
When 2 and 3 are already in use
Which positions are the same on a benzene no?
2 and 6
3 and 5
What does TCP stand for and what is it used in?
Trichloro phenol
Disinfectants
During the electrophilic addition reaction of bromine with a halogen, what forms?
Major and minor products
What is the major product formed from when major and minor products can form? Why?
Major product formed from the secondary carbocation
Secondary carbocation is more stable than the primary one
Secondary carbocation
Positive charge attached to a carbon atom attached to 2 carbon atoms
Conditions for free radical substitution
UV light
Structural isomerism vs stereoisomerism
Structural isomerism: concerned with the position of atoms in a molecule
Stereoisomerism: concerned with the position atoms take up in space
