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OCR A-Level Chemistry A > Chapter 26 - Carbonyls and Carboxylic Acids > Flashcards

Chapter 26 - Carbonyls and Carboxylic Acids Flashcards

Carbonyl compounds, Identifying aldehydes and ketones, Carboxylic acids, Carboxylic acid derivatives.

1
Q

what is the double bond in the carbonyl and alkene functional group made of?

A

The double bond in the carbonyl and alkene functional group is made of a σ (sigma) bond and a π bond. the sigma bond is formed by the overlap of orbitals between the C and O atoms. the pie bond is formed by the carbon and oxygen p orbitals.

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2
Q

What is the carbonyl functional group?

A

the carbonyl group is C=O

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3
Q

what is an aldehyde?

A

aldehydes have the functional group CHO and a suffix of ‘al’.

H-C=O

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4
Q

what is a ketone?

A

a ketone ends in the suffix ‘one’ and functional group is CO
looks like this:
C
C=O
C

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5
Q

What is the reaction and conditions for oxidation of aldehydes?

A

the condition are it must be done In reflux
with a K2Cr2O7 / H2SO4 catalyst

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6
Q

Outline the detection of a carbonyl group using Brady’s reagent?

A

To detect carbonyl (C=O) compounds…
Add 2,4 DNPH (Brady’s reagent)
AIf a yellow/orange precipitate indicates a carbonyls presence

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7
Q

Which reagent can distinguish between an aldehyde and a ketone?

A

Tollen’s reagent reacts with an aldehyde only

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8
Q

is the double bond = polar or nonpolar?

A

1) The C=C ( alkene group) is non polar
2) The C=O (carbonyl group) is polar

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9
Q

How does Tollen’s reagent distinguish between an aldehyde and a ketone?

A

If an Aldehyde group is present a Silver (Ag) mirror is produced. If no Ketone group is present then no silver mirror is produced.

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10
Q

How does Fehling’s reagent distinguish between an aldehyde and ketone?

A

If an Aldehyde group is present a Brick red precipitate is formed. If a Ketone group is present it stays blue/no change

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11
Q

what to and how are aldehydes reduced to?

A

aldehydes are reduced by NaBH4 to secondary alcohols.

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12
Q

what to and how are ketones reduced?

A

Ketones are reduced by NaBH4, to secondary alcohols

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13
Q

outline the reaction of carbonyl compounds with HCN?

A

hydrogen cyanide HCN adds across the C=O bond of aldehydes and ketones to form a hydroxynitrile ( containing a -OH and -CN functional groups) HCN is a poisonous gas. HCN is made from sodium cyanide NaCN and sulferic acid H2SO4

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14
Q

outline the reaction mechanism for nucleophilic addition of NaBH4 to carbonyl compounds?

A
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15
Q

outline the mechanism for a carbonyl compound reacting with NaCN/H+ ?

A

in this reaction, the nucleophile is the cyanide ion, :CN- ( from the NaCN)

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16
Q

How can acidified potassium dichromate distinguish between aldehydes and ketones?

A

If an Aldehyde is present solution turns from Orange to green.
If a ketone is present there’s no change to solution.

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17
Q

Why is potassium cyanide used instead of hydrogen cyanide?

A

It’s safer

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18
Q

how soluble is carboxylic acid?

A

The C=O and O-H bonds in carboxylic acid are polar allowing it to form hydrogen bonds with water.

1) carboxylic acids are only soluble up to 4 carbon atoms
2) solubility decreases as carbon chain increases because the carbon chain is non polar

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19
Q

how strong are carboxylic acids?

A

carboxylic acids are weak acids and only partially dissolve in water

RCOOH (aq) = H+ + RCOO-

20
Q

carboxylic acid + metal = ?

A

in aqueous solution carboxylic acids react with metals to form a carboxylate salt and hydrogen gas.

e.g 2CH3COOH (aq) + Mg(s) = (CH3COO-)2 Mg2+ + H2 (g)

21
Q

carboxylic acids + metal oxides =?

A

carboxylic acids react with metal oxides to form a salt and water.

e.g 2CH3COOH + MgO = (CH3COO-)2Mg2+ + H2O

22
Q

carboxylic acids + alkalis = ?

A

carboxylic acids react with alkalis to form a salt and water

e.g CH3COOH + NaOH = CH3COO-Na+ + H2O

23
Q

carboxylic acid + carbonates = ?

A

carboxylic acids react with carbonates to form a salt, CO2 and H2O

e.g 2 CH3COOH + Na2CO3 = 2CH3COO-Na+ + CO2 + H2O

24
Q

Name the four carboxylic acid derivatives

A

1) Ester
2) Acyl chloride
3) Acid anhydride
4) Amide

25
Q

how do you name esters?

A

1) ‘oic acid’ suffix is removed and replaced with ‘oate’
2) The alkyl chain attached to the COO group is then added to th first word

26
Q

how do you name an acyl chloride?

A

replace ‘oi acid’ with ‘oyl chloride’ and boom its done

27
Q

how do you name an acid anhydride?

28
Q

When an acid anhydride reacts with a nucleophile, what are the two products?

A

R-CONu
R-COO-

29
Q

What is the characteristic mechanism to change an acyl chloride to a carboxylic acid?

A

Addition-Elimination

30
Q

what is esterification?

A

esterification is the reaction of an alcohol with a carboxylic acid to form an ester. ester has a RCOOR
an Alcohol is warmed with carboxylic acid and conc sulfurated acid is added as a catalystt

31
Q

what is hydrolysis ?

A

hydrolysis is the chemical breakdown of a compound in the presence of water or in an aqueous solution.

32
Q

what is acid hydrolysis of an ester?

A

acid hydrolysis is the reverse reaction of esterification

  1. Ester is heated under reflux with dilute aqueous acid
  2. Ester broken down by water into carboxylic acid and alcohol
33
Q

what is alkaline hydrolysis of an ester?

A

alkaline hydrolysis is irreversible. the ester is refluxed with aqueous alkali.

  1. Ester heated under reflux with aqueous alkali (hydroxide ions )
  2. Ester is broken down by water into carboxylate ion and alcohol
34
Q

how to prepare an acyl chloride?

A

acyl chlorides can be prepared by reacting a carboxylic acid + thionyl chloride, SOCl2

35
Q

acyl chloride + alcohol = ?

36
Q

how to form esters from acyl chlorides?

A

acyl chloride + alcohol = aliphatic ester + HCl

acyl chloride phenol = aromatic ester + HCl

37
Q

how to form carboxylic acids from acyl chlorides?

A

acyl chloride + water = carboxylic acid + HCl

38
Q

how to form amides from acyl chlorides?

A

acyl chloride + ammonia (NH3) = primary amide + NH4+Cl-

acyl chloride + amine = secondary amide + CH3NH3+Cl-

39
Q

how do acid anhydrides react with alcohols, phenols,water, ammonia and amies?

A

acid anhydrides react with alcohols, phenols,water, ammonia and amines the same way acyl chlorides do

40
Q

whats the equation for for the formation of phenyl ethanoate?

41
Q

What’s the carboxyl group?

A

a carbonyl group + hydroxyl group= carboxyl group.

carboxyl group is COOH HO-C=O

42
Q

whats an ester?

A

An ester is where a carboxylic acids Hydrogen in the OH group is replaced by a carbon making a C-O-C bond.its named after its parent carboxylic acid. to name an ester remove the suffix oic acid and replace it with ‘oate’

43
Q

What is an acyl chloride?how do you name it?

A

in an acyl chloride the OH in a carboxylic acid is replaced by a cl group its now a O=c-Cl . its named after its parent carboxylic acid from which its derived. To name an acyl chloride remove the ‘oic acid’ suffix and replace it with ‘oyl chloride’

44
Q

What is an acid anhydride? how do you name it?

A

An acid anhydride is when two carboxylic acids are sharing an oxygen instead of having an oh group. its named by removing the ‘acid’ and putting the suffix ‘anhydride’

45
Q

whats an amide?

A

an amide is when the OH group on a carboxylic acid is replaced by an ‘NH2’. it looks like a O=C-NH2

46
Q

whats an ether?

A

ether has a functional group COC

47
Q

whats a dimer?

A

A structure containing two identical or similar units

OCR A-Level Chemistry A (33 decks)

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