Organic Chemistry Flashcards
what is optical isomerism?
- same structural formula, different arrangement of atoms in space
- mirror images of each other
- have chiral carbon atom
what is a chiral carbon?
has 4 different groups attached
what are enantiomers?
molecules that are mirror images of each other and are non-superimposable
how can you tell if isomers are optically active?
will rotate plane polarised light
what is a racemic mixture?
mixture with equal amounts of each enantiomer
why don’t racemates rotate plane polarised light?
2 enantiomers rotate light in opposite directions + they cancel out
what are aldehydes oxidised to?
carboxylic acids
outline how tollens reagent is made
add a few drops of NaOH and a few drops of dilute NH3 to silver nitrate until the pale brown ppt dissloves
what can tollens reagent be used for? how?
- testing for aldehydes and ketones
- aldehydes: tollens reduced to silver mirror
- ketones: no ppt formed
what can Fehling’s solution be used for? how?
- test for aldehydes and ketones
- add warm to aldehyde/ketone
- aldehyde will turn blue solution to red red ppt (Cu2)
- ketone solution remain blue
name one reducing agent used to reduce aldehydes/ketones? what is formed?
- NaBH4
- primary (aldehydes) or secondary alcohols (ketones)
what is esterification?
formation of esters by reacting alcohols with carboxylic acids or acid anhydrides
give a word equation for the production of an ester from an alcohol and carboxylic acid. include the name of the catalyst
carboxylic acid + alcohol –sulfuric acid–> ester + water
give a word equation for the production of an ester from an alcohol and acid anhydride
acid anhydride + alcohol —-> ester + carboxylic acid
give an example of an ester. which alcohol and carboxylic acid is required to make this?
methyl ethanoate
methanol + ethanoic acid
what are the uses of esters?
- perfumes + food flavourings
- solvents -> polar so compounds will dissolve readily in esters
- glues -> low bp + evaporate easily
- plasticisers
what are the conditions required for the acid hydrolysis of esters? what is produced?
- dilute acid (sulfuric/HCl)
- reflux
- carboxylic acid + alcohol
what are the conditions required for the base hydrolysis of esters? what is produced?
- dilute base, e.g. NaOH
- reflux
- carboxylate ion + alcohol
what is the IUPAC name for glycerol?
propane-1,2,3-triol
give an example of a fat or oil with unsaturate hydrocarbon chains?
vegetable oils
what are the properties of oils/fats with unsaturated hydrocarbon chains? why?
- liquids at room temp
- chains not straight = can’t pack closely together = weaker vdw = lower mp
give an example of an oil/fat with saturated hydrocarbon chains
animal fats
what are the properties of oils/fats with saturated hydrocarbon chains?
- solids at room temp
- staight + more uniform chains = can pack closely together = stronger vdw = higher mp
how can soap be produced? give a word equation.
hydrolysing animal fats and vegetable oils by heating with NaOH
fat + sodium hydroxide –> glycerol + soap (sodium salt)
what is biodiesel? how can it be produced? give a word equation.
- mixture of fatty acids made from methyl esters + can be made from rapeseed oil
- reacting vegetable oils with methanol with a potassium hydroxide catalyst
oil + methanol –> glycerol + methyl ester
what is the functional group of acyl chlorides?
-COCl
give an example of an acyl chloride
ethanoyl chloride
CH3-C\Cl=O
what does the reaction of acyl chlorides with water produce? give a word equation for the reaction of ethanoyl chloride and water.
ethanoyl chloride + water –> ethanoic acid + HCl
what does the reaction of acyl chlorides with ammonia produce? give a word equation for the reaction of ethanoyl chloride and ammonia.
amides
ethanoyl chloride + ammonia –> ethanamide + HCl
what does the reaction of acyl chlorides with alcohol produce? give a word equation for the reaction of ethanoyl chloride and methanol.
esters
ethanoyl chloride + methanol –> methyl ethanoate + HCl
what does the reaction of acyl chlorides with primary amines produce? give a word equation for the reaction of ethanoyl chloride and methylamine.
ethanoyl chloride + methylamine –> N-methylethanamide + HCl
what is an acid anhydride?
molecule made from 2 carboxylic acids that are the same
give an example of an acid anhydride
ethanoic anhydride
which reactions are more vigorous, acyl chloride reactions or acid anhydride reactions
acyl chloride reactions
what does the reaction of acid anhydrides with water produce? give a word equation for the reaction of ethanoic anhydride and water.
carboxylic acids
ethanoic anhydride + water –> ethanoic acid + ethanoic acid
what does the reaction of acid anhydrides with ammonia produce? give a word equation for the reaction of ethanoic anhydride and ammonia.
amides
ethanoic anhydride + ammonia –> ethanamide + ethanoic acid
what does the reaction of acid anhydrides with alcohol produce? give a word equation for the reaction of ethanoic anhydride and methanol.
esters
ethanoic anhydride + methanol –> methyl ethanoate + ethanoic acid
what does the reaction of acid anhydrides with primary amines produce? give a word equation for the reaction of ethanoic anhydride and methylamine.
N-substituted amides
ethanoic anhydride + methylamine –> N-methylethanamide + ethanoic acid
by what mechanism do acyl chlorides react?
nucleophilic addition elimination
why are acyl chlorides susceptible to attack from nucleophiles?
have a strong partial negative on the carbon, as oxygen/chlorine atoms are electronegative
outline nucleophilic addition elimination
- nucleophile attacks partially pos carbon
- e move from double bond to oxygen
- e move from oxygen to the bond
- e move from bond to chlorine
- e move from detached chlorine to a hydrogen
what is aspirin? how is it made?
ester made by reacting ethanoic anhydride or ethanoyl chloride + salicylic acid
why is ethanoic anhydride is used instead of ethanoyl chloride in industry?
- safer as less corrosive, doesnt produce harmful HCl gas and doesnt react vigorously with water
- cheaper
describe the structure of benzene
- cyclic, planar molecule
- each carbon is bonded to 2 other carbons and 1 hydrogen atom
- e form delocalised e ring
- all C-C bond same length
why is benzene more stable than the theoretical alternative cyclohexa-1,3,5-triene?
- measure stability by comparing enthalpy change of hydrogenation in both
- if cyclohexene hydrogenated has enthalpy change of -120 so benzene expected to have -360 due to 3 double bonds but actually has -208
- suggests more energy is required to break bonds = more stable due to delocalised e structure
what are aromatic compounds/arenes?
molecules that contain a benzene ring
what kind of reactions do aromatic compounds/arenes undedrgo?
electrophilic substitution
why does benzene not undergo electrophilic addition reactions?
stable
list 2 types of electrophilic substitution
- friedel crafts acylation
- nitration
what is friedel crafts acylation?
acyl chloride and halogen carrier (AlCl3) react to create a strongly positive electrophile
why is friedel crafts acylation necessary?
- stability makes benzene harder to react
- adding acyl group makes benzene molecule weaker
give an equation for friedel crafts acylation
RCOCl + AlCl3 –> RC+=O + AlCl4-
outline the mechanism for friedel crafts acylation (what to draw)
- arrow from circle in benzene ring to RC+=O
- arrow from AlCl4- to RC+=O
- R-C-benzene ring with =O on c + HCl + AlCl3
what is nitration of benzene used for?
making dyes and explosives
what conditions are required for the nitration of benzene?
- conc nitric acid
- conc sulfuric acid
- 50c
give 2 equations for the reactions that take place before the nitration of benzene
- HNO3 + H2SO4 –> H2NO3+ + HSO4-
- H2NO3+ –> NO2+ + H2O
outline the mechanism for the nitration of benzene (what to draw)
- arrow from circle in benzene e ring to +NO2
- NO2 attached to benzene, arrow from H on benzene to half benzene e ring with + in middle
3 NO2 attached to benzene + H+ (to react with HSO4- to regenerate catalyst)
how does temperature affect the nitration of benzene?
- temp below 55c will ensure a single NO2
- above will result in multiple substitutions
what kind of molecule is phenylamine?
aromatic primary amine
