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Chemistry OCR A > Chapter 26 Carbonyls > Flashcards

Chapter 26 Carbonyls Flashcards

1
Q

What is a carbonyl compound, aldehyde and ketone?

A

Carbonyl- any compound contain a C=O
Aldehyde- C=O at the end of a compound (aka 1 hydrogen still attached to the carbon of the C=O)
Ketone- C=O anywhere other than the end of a compound

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2
Q

How do you name aldehydes and ketones?

A

Aldehydes- end with al, if prefix, formyl
Ketones- end with one, if prefix, oxo

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3
Q

How can aldehydes be oxidised, give an equation?

A

React with Na2Cr2O7 and H+, heat under reflux, carboxylic acid

Aldehyde + [O] —/ Carboxylic Acid

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4
Q

Why can ketones not be oxidised?

A

The contain no hydrogens that can be lost, directly attached to the C of the C=O

(Oxidation=loss of hydrogen as well)

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5
Q

Why can carbonyl compounds undergo nucleophilic addition?

A

C=O polar, slight positive of the carbon
Nucleophiles attack carbon, lone pair upon oxygen, can be easily protonated

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6
Q

What are the conditions, reagents, and equation for the reduction of a carbonyl?

A

Carbonyl + 2[H] –/ Alcohol
React with aqueous NaBH4 (Effectively hydride ions, need water)

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7
Q

What are the conditions and reagents for producing a hydroxynitrile from a carbonyl?

A

React with H2SO4/NaCN to produce HCN
In situ as HCN poisonous
Protonated by acid

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8
Q

What compound detects carbonyl compounds and what occurs? Give the specific components on the reactant.

A

2,4 DNP in methanol and Sulphuric acid / Brady’s reagent
Pale orange to a yellow/orange precipitate
Condensation reaction between hydrazine and carbonyl, with C=O replaced with C=N

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9
Q

How can using 2,4 DNP help determine the identity of the carbonyl compound?

A

The precipitate is a 2,4 dinitrohydrozone derivative
Purify by filtering under reduced pressure, recrystallising, filter again
Check the melting point of the compound and compare to the data base

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10
Q

How can you detect an aldehyde instead of a ketone?

A

Add Tollen’s reagent, AgNO3 in NH3
AND HEAT IN A WATER BATH
Aldehydes can be oxidised into carboxylic acids, Ag+ is reduced to Ag, acting as oxidising agents
So a silver mirror is produced
Ketones cannot be oxidised further so the solution remains colourless

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11
Q

What are carboxylic acids? How do you name carboxylic acids?

A

R- COOH
Always the highest priority, only carboxy on a side chain
-Oic Acid, no need to number at starting from 1
e.g 3-hydroxybutanoic acid

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12
Q

Why are carboxylic acids soluble in water?How does solubility change as the carbon chain gets longer?

A

Hydroxyl and Carbonyl can form hydrogen bonds with water
Increasing the chain length increases the contribution of the non-polar carbon chain, contribution of polar carboxyl decreases
So less soluble

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13
Q

What happens when carboxylic acids are in water?

A

They partially disassociate, weak acids
Resonance stabilised carbanion

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14
Q

What are the acid reactions of carboxylic acids?

A

React with a metal to form a salt and hydrogen, fizzing, disapears
React with metal oxides/hydroxides to form salt and water, disappears
React with metal carbonates to form salt, CO2 and water- fizzing, disappears- organic test for COOH

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15
Q

What are esters? How do you name them?

A

R-COO-R’
Chain of C=O is -oate, other side is alkyl chain
If functional groups on chain, start numbering from carbon joined to the O, treat as two separate chains, two different numbers

e.g methyl propanoate
3-chloro-2-methybutyl 2-bromopropanoate

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16
Q

How do you form esters from alcohols and carboxylic acids?

A

React with acid (sulphuric) catalyst
Forms ester and water, condensation reaction
Reflux, warm

17
Q

What is acid hydrolysis of esters?

A

React the ester with aqueous sulphuric acid and heat under reflux
Reforms alcohol and carboxylic acid
Reversible reaction, same products as previous reactants and catalyst

18
Q

What is the alkaline hydrolysis of esters?

A

Heat under reflux with NaOH
Forms a carboxylate salt (if named hydroxide used) or carboxylate ion, resonance stabilised
And alcohol
Irreversible
Also called saponification

19
Q

What are acid anhydrides? How do you name acid anhydrides?

A

R-C-OOOC-R’
If the same on either side, just once, ethanoic anhydride
If different list in alphabetical
e.g Methanoic Propanoic Anhydride

20
Q

How can you produce an ester using an acid anhydride?

A

Ethanoic Anhydride + Butan-1-ol —/ Butyl Ethanoate + Ethanoic Acid

Produces ester and carboxylic acid, no catalyst needed

21
Q

How can you produce an ester using an acyl chloride?

A

Ethanoyl Chloride + Butan-1-ol –/ Butyl Ethanoate + HCl

No catalyst, ester + HCl

22
Q

How can you make an ester, 3 ways?

A

Alcohol + Carboxylic Acid
Alcohol + Acid Anhydride
Alcohol + Acyl Chloride

23
Q

What can form an ester with phenol?

A

Acid Anhydrides and Acyl Chlorides- reactive enough
NOT Carboxylic Acids

24
Q

What is the order of reactivity of carbonyls?

A

Carboxylic Acid < Acid Anhydride < Acyl Choride

25
Q

How can you make acyl chlorides from carboxylic acids? Give an equation

A

Reaction with thionyl chloride SOCL2

Carboxylic acid + SOCl2 —/ Acyl Chloride + SO2 + HC

Needs to be done in a fume hood, toxic gases

26
Q

What is an acyl chloride? How do you name them?

A

C=O bonded to a more electronegative element
Acyl Chloride- C=O bonded to Cl
Very reactive

Ethanoyl Chloride

27
Q

What are the main 3 reactions of acyl chlorides and acid anhydrides?

A

With water to form carboxylic acids
With amines/NH3 to form amides
With alcohols to form esters

28
Q

What is the reaction between an acyl chloride and ammonia?

A

Acyl Chloride + 2NH3 —/ Primary Amide + NH4Cl

29
Q

What is the reaction between an acyl chloride and an amine?

A

Acyl Chloride + 2CH3NH2 —/ CH3NHCOR + CH3NH3+Cl-

Acyl Chloride + Amine —/ Secondary Amide + carbammonium salt

30
Q

What is the reaction between an acyl chloride and water?

A

Acyl Chloride + H2O —/ Carboxylic Acid + HCl

vigorous, steamy toxic fumes

31
Q

How are carboxylic acids reduced, and what is formed?

A

LiAlH4
Form primary alcohols

32
Q

Do carboxylic acid derivatives react with 2,4 DNP?

A

No, only aldehydes and ketones
No other carbonyls as resonance stabilised by the lone pair

33
Q

Can carboxylic acids react with ammonia?

A

Yes- normally acid-base reaction

Rate too slow normally to form amides but think about condensation polymers, polyamides

Depends on conditions

34
Q

What are the steps for using 2,4 DNP?

A

Brady’s reagent, 2,4DNP in methanol and sulphuric acid
Add an excess to a test tube
Then adda few drops of the organic compound and see if crystals form
Then add H2SO4 if crystals still do not form

An orange precipitate suggests a carbonyl

35
Q

Why does methanoic acid dissolve in water? How does this relate to the methanoate ion?

A

Polar O-H bond and C=O, forms hydrogen bonds with water

Methanoate ion not rly a large factor when it comes to dissolving as so few disassociate

Chemistry OCR A (28 decks)

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