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OCR Chemistry A > 6.1.2&3 - Carbonyl Compounds and -COOH > Flashcards

6.1.2&3 - Carbonyl Compounds and -COOH Flashcards

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1
Q

Bond angle in carbonyl compounds

A

Trigonal Planar (120)

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2
Q

How are sigma bonds formed

A

Direct overlap of orbitals

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3
Q

Bonding and structure in carbonyl compounds

A

p-orbital overlapping sideways

Forms pi-orbital

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4
Q

Nucleophilic addn in carbonyls

A

Nu-H -C=O
-C-O-H
I
Nu

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5
Q

Boiling points of carbonyls

A

Ald < Alc < Acid
Low –> High
Ketones and aldehydes lack hydroxyl groups and so are incapable of H bond
Presence of only one oxygen in alc vs. two in acid

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6
Q

Brady’s Reagent

A

2,4-DNP

2,4 dinitrophenyl hydrazine

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7
Q

Reaction w/ Brady’s Reagent

A

Reacts w/ carbonyl group to form an orange ppt and water

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8
Q

Why does Brady’s not work w/ carboxylic acids

A

Not electrophilic enough in comparison to ketone and aldehyde

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9
Q

How to determine the identity of a specific carbonyl compounds

A

Add 2,4-DNPH and obtain orange ppt
Filter, recrystallise, filter and dry
Find mp of the 2,4-DNP derivative
Reference to a database of values

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10
Q

Tollens Reagents

A 
2 Ag(NH3)2 ^+
Silver nitrate dissolved in ammonia
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11
Q

Reaction w/ Tollens if an aldehyde is present

A

Ag+ is reduced to Ag metal and creates a silver ‘mirror’ on the side of the test tube
Does not occur w/ ketones as it needs a hydrogen

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12
Q

Why is the reaction w/ Tollens redox

A

Ag+ is reduced to Ag and the aldehyde is oxidised to COOH

RCHO + [O] —>RCOOH

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13
Q

Carboxylic acid and metal —>

A

Salt and H2

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14
Q

Carboxylic acid and Metal oxide —>

A

Salt and H2O

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15
Q

Carboxylic acid and Base —>

A

Salt and H2O

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16
Q

Carboxylic acid and Carbonate —>

A

Salt and CO2 and H2O

17
Q

Nucleophilic addn. of aldehydes (reduction)

A

Aldehyde + 2[H] —> primary alcohol

NaBH4/ H2O (warm)

18
Q

Nucleophilic addn. of ketones (reduction)

A

Ketone + 2[H] —> secondary alcohol

NaBH4/ H2O

19
Q

What allows nucleophilic addn in carbonyls

A

O is more elctro-ve therefore electron density in bond lies closer to O than C
C is electron-deficient and attacked by nucleophiles as they’re electron pair donors.

20
Q

Carbonyl compounds + HCN (addn. reactions)

A

(H2SO4/ NaCN)
C=O —-> - C- CN
I I
H OH

21
Q

Why is it useful to react carbonyl compounds w/ HCN

A

Can increase carbon chain lengths

22
Q

Hydroxynitriles

A

Cyanohydrins

Have 2 functional groups -OH (hydroxyl) and C triple bond N (nitriles)

23
Q

Nucleophilic vs Electrophilic addn

A

If the organic compound is an electrophile, its nucleophilic addn
If the organic compound is a nucleophile, it’s electrophilic addn

24
Q

Aldehyde and acidified dichromate —->

A

(Under reflux) - Carboxylic acid

25
Q

Esterification

A

Reacting an alcohol w/ a carboxylic acid w/ conc. H2SO4 (warm) - also makes H2O
Acid anhydrides w/ alcohol (works w/ phenol - also makes -COOH

26
Q

Acid hydrolysis of esters

A

Reversible equation
Ester is heated under reflux w/ dilute aq acid (HCl)
Broken by water w/ acid as catalyst
Reforms monomers

27
Q

Alkali hydrolysis of esters

A

Irreversible reaction
Reacted with NaOH/KOH (aq) under reflux
Ethyl propanoate + KOH —> Potassium propanoate + ethanol

28
Q

Making esters from acyl chlorides

A

Acyl chloride + alcohol (nucleophile)—> Ester + HCl

29
Q

Making acyl chloride

A

Carboxylic acid + thionyl chloride (SOCL2) –> Acyl chloride + sulfur dioxide + HCl

30
Q

Naming amides

A

N (side chain attached to N) (side chain attached to carbonyl ) amide

31
Q

Test to distinguish -COOH and esters

A

Add NaHCO3/ Na2CO3
-COOH : effervescence (CO2 given off)
Ester: no effervescence

32
Q

Reduction using NaBH4

A

Adds an H

oxidation removes an H/O

33
Q

How are acid anhydrides formed

A

Two molecules of a carboxylic acid

34
Q

What are carboxylic acid salts called

A

Carboxylate

35
Q

Formation of carboxylate salts

A
  • COOH + NaOH —> -COO-Na+ +H2O
  • COOH + Na —> -COO-Na+ + 1/2 H2
  • COOH + Na2CO3 —> -COO-Na+ + CO2 + H2O
36
Q

Why are acyl halides very strong electrophiles

A

Halogens are more electronegative and the lone pair doesn’t delocalise onto the carbonyl bond
Leaves C very electron deficient so prone to attack by a nucleophile

37
Q

Strongest to weakest electrophiles

A

Acid anhydride/ acyl halide
Ketones/ aldehyde
Ester, -COOH, amides

38
Q

Why are acid anhydrides strong electrophiles

A

The lp gets split between both groups

39
Q

Why are ester, -COOH and amides weak electrophiles

A

The lp is delocalalised over the OCO bonds, reducing electron deficiency on C

OCR Chemistry A (16 decks)

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