4.1.2 CARBONYL COMPOUNDS

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How do you make a carbonyl?
oxidise an alcohol (1 or 2) with acidified potassium dichromate/ dichromate ion is reduced/ colour change from orange to green
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Describe the oxidation of a primary alcohol to an aldehyde
reaction has to be controlled as too much [o] can result in an COOH/ controlled conditions/ remove aldehyde as soon as formed/ gently heat OH with controlled count of [o] and acid in distillation apparatus
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Outline distillation apparatus
...
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Describe the oxidation of a secondary alcohol
OH heated under reflux
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Outline reflux apparatus
...
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Describe the formation of carboxylic acids from aldehydes - why is it done under reflux?
oxidation/ heated under reflux/ excess [o]/ reflect enables temps to be risen w/o loosinh volatile solvents/ any vaporised compounds cool condense and drip back in
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Describe the reduction of aldehydes and ketones
nucleophilic addition/ NaBH4 produces nucleophile H-/ H2O involved/ produces alcohol and OH-
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What is the test for carbonyl compounds?
Brays reagent/ 2,4-DNP/ 2,4-dinitrophenyl hydrazine/ ethanol + 2,4-DNP/ ppt bright orange
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How can a carbonyl compound be identified from 2,4-DNP ppt?
ppt is a derivative of the carbonyl compound/ each compound produces a different derivative with a different melting point/ compared against known mp it can be identified
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What is Tollens' reagent? what is it used for?
colourless solution of silver nitre (AlNO3) dissolved in aqueous ammonia/ distinguish between aldehydes and ketones/ ammoniacal silver nitrate
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Outline the Pollens' test
aldehydes can be oxidised into COOH/ Tollens' [o] heated in a test tube/ if aldehyde present silver mirror is fomred/ Ag+ reduced to Ag (s)
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Card 2

Front

Describe the oxidation of a primary alcohol to an aldehyde

Back

reaction has to be controlled as too much [o] can result in an COOH/ controlled conditions/ remove aldehyde as soon as formed/ gently heat OH with controlled count of [o] and acid in distillation apparatus

Card 3

Front

Outline distillation apparatus

Back

Preview of the front of card 3

Card 4

Front

Describe the oxidation of a secondary alcohol

Back

Preview of the front of card 4

Card 5

Front

Outline reflux apparatus

Back

Preview of the front of card 5
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