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”