17.6 Flashcards by bethany loughead

how can bromoethane be converted to ethyl propanoate give conditions reagents and the types of reactions

bromoethane -> ethanol
reflux with aqueous potassium hydroxide
hydrolysis reaction
ethanol -> ethyl propanoate
heat with propanoic acid using an acid catalyst
esterification reaction

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give 4 ways you can extent the length of a carbon chain

react a halogenoalkane with cyanide ion to form a nitrile
addition of hydrogen cyanide to a carbonyl compound
alkylation of benzene
grinard reagents

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what are Grignard reagents

organometallic compounds containing magnesium

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how are Grignard reagents formed

halogenoalkane/haloarene heated under reflux with magnesium and a solvent of dry ether

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what is the general equation for the formation of a Grignard reagent

R-Br + Mg -> R-Mg-Br

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what is formed and what is the equation for the reaction of a Grignard reagent with carbon dioxide

carboxylic acid
RMgBr -> RCOOH

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what is formed and what is the equation for the reaction of a Grignard reagent with methanal

primary alcohol
RMgBr -> RCH2OH

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what is formed and what is the equation for the reaction of a Grignard reagent with an aldehyde (R’CHO)

secondary alcohol
RMgBr -> RR’CHOH

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what is formed and what is the equation for the reaction of a Grignard reagent with a ketone (R’COR’’)

tertiary alcohol
RR’R’‘COH

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when can Grignard reagent reactions be used to increase straight chain length

reaction with carbon dioxide and methanal

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when can Grignard reagents be used to create branched molecules

reaction with aldehydes and ketones

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define hazard

property of a substance that could cause harm to a user

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what is a risk

the possible effect that a substance may cause to a user, this will depend on factors such as concentration and apparatus

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what are mercury thermometers often replaced by to reduce risk

digital thermometer

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how can you reduce risk of using a Bunsen burner

use a heating mantle instead

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how can you reduce risk when heating volatile organic compounds

heat under reflux to stop the reaction mixture escaping from the reaction with a reflux condenser

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where does the water enter and leave a reflux condenser

enters at the bottom near the reaction mixture and leaves at the top

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how can you separate an impure liquid using simple distillation

heat it in a flask connected to a condenser and the liquid with the lowest boiling temperature will pass into the condenser first and is collected in the receiver separately from the rest of the mixture

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why is the thermometer important in simple distillation

because it monitors the temperature of the vapour, if temp remains steady it indicates 1 compound is being distilled off and when the temperature begins to rise another compound will be beginning to be distilled

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what are the advantages and disadvantages of using simple distillation

+/ easier to set up
faster
-/ does not separate liquid as well as fractional distillation
can only be used if the bp of the liquids is significantly different (<25)

what does steam distillation do

separates insoluble liquid from an aqueous solution

how is steam distillation carried out

pass steam into a reaction mixture that contains an aqueous solution and a separate liquid layer
the top liquid evaporates and is collected in the receiver

what are the advantage of steam distillation

insoluble liquid is removed from the reaction mixture below its normal boiling temperature

what is the advantage of using steam distillation with phenylamine

the temperature at which the phenylamine distils is much lower than its boiling temperature so there is less chance of decomposition

why has the fractioning column got glass beads in it

act as a surface on which the vapour leaving the column can condense and evaporate again so that repeated distillation occurs as it passes up the column which provides better separation

what does immiscible mean

doesn't form a mixture

what must the properties of the solvent be for solvent extraction

should be immiscible with the original solvent desired product must be more soluble in it than the original solvent

describe solvent extraction

- place reaction mixture in a separating funnel than add chosen solvent in small proportions as this is more effective - agitate mixture by inverting funnel multiple times - allow contents to separate into 2 layers - remove stopper and open tap to allow lower layer to drain out - then drain the top layer into a separate flask

what is always the next step after solvent extraction

simple or fractional distillation

how can washing be used to get a pure solid

stir impure solid with solvent which dissolves impurities but as little substance as possible then filter out the now pure solid

how can washing be used to get a pure liquid

mix the mixture with a solvent which dissolves the impurities but not the substance then separate with solvent extraction (separating funnel)

state some common drying agents

calcium chloride magnesium sulfate sodium sulfate

how do drying agents work

the anhydrous metal salts form hydrated salts when they come into contact with water so absorb water as water of crystallization

what is observed when a drying agent is used

begins powdery than goes more crystalline

how do you know the organic liquid is dry when using drying agents

if more drying agent is added and remains powdery it indicated that the liquid is dry

what is the main piece of apparatus needed for filtration

Buchner funnel

summarise the steps in recrystallisation

- add impure solid to conical flask - add chose solvent and warm to near boil - continue this until the solute has fully dissolved - if insoluble impurities are left then these must be filtered out - allow liquid to cool until crystals have formed - dry further with Buchner funnel

how can you check a compound is pure

if solid - measure melting temperature if liquid - measure boiling temperature

why is chromatography used

to separate a mixture into its individual components to identify the components of a mixture

why must a lid be placed on the container for paper chromatography

to prevent evaporation of the solvent

what is the stationary phase in paper chromatography

the liquid or solid that does not move

what is the mobile phase in paper chromatography

the liquid that moves through the stationary phase and transports the components

if a component moves far up the paper what is its attraction to the mobile and stationary phase

strongly attracted to the mobile phase weakly attracted to the stationary phase

if a component does not move far up the paper what is its attraction to the stationary and mobile phase

strongly attracted to the stationary phase weakly attracted to the mobile phase

what is the stationary and mobile phase of paper chromatography

stationary - water trapped in the fibers of the chromatography paper mobile - solvent

what is the equation for Rf value

distance travelled by solute/distance travelled by solvent

what does Rf stand for

retention factor

whats the difference between paper chromatography and thin layer chromatography

TLC uses a sheet of plastic or glass coated in silica or alumina instead of paper

what is the advantage of using column chromatography

larger quantities of material can be separated