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chemistry ocr a a level > 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.

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1
Q

What is the carbonyl functional group?

A

C=O

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2
Q

What is the reaction condition and reactants for oxidation of aldehydes?

A

In reflux
K2Cr2O7
H2SO4

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3
Q

Outline the detection of a carbonyl using Brady’s reagent

A

Add 5cm depth of 2,4 DNPH (Brady’s reagent)
Use a pipette to add three drops of unknown
If no crystals form, add a few drops of sulphuric acid
A yellow/orange precipitate indicates carbonyl presence

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4
Q

Which reagent can distinguish between an aldehyde and a ketone?

A

Tollen’s reagent

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5
Q

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

A

Aldehyde group present
Silver mirror produced
Ketone group present
No silver mirror produced

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6
Q

Outline nucleophilic addition with a carbonyl and cyanide ion

A

Negative charge cyanide attacks the electron deficient carbon atom
Lone pair from -CN to C to form dative covalent bond

Lone pair from C=O to O by heterolytic bond fission
O- lone pair to H on HCN
Lone pair in H-C to C in CN
OH formed
Nitrile formed
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7
Q

How can acidified potassium dichromate distinguish between aldehydes and ketones?

A

Aldehyde present
Orange solution to green
Ketone present
No change to solution

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8
Q

Why is potassium cyanide used instead of hydrogen cyanide?

A

It’s safer

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9
Q

Name the four carboxylic acid derivatives

A

Ester
Acyl chloride
Acid anhydride
Amide

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10
Q

What is the suffix for an acyl chloride?

A

-oyl chloride

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11
Q

What is the suffix for an acid anhydride?

A

-oic anhydride

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12
Q

Describe esterification

A

Alcohol + carboxylic acid with conc sulfurated acid

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13
Q

Outline process of acid hydrolysis of an ester

A

Ester heated under reflux with dilute aqueous acid

Ester broken down by water into carboxylic acid and alcohol

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14
Q

Outline process of alkaline hydrolysis of an ester

A

Ester heated under reflux with aqueous hydroxide ions

Ester broken down by water into carboxylate ion and alcohol

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15
Q

Describe the reaction of carbonyl compounds with NaBH4 and butanal

A

butanal + 2[H]&raquo_space;»> butan-1-ol

In the presence of NaBH4/H20

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16
Q

reducing agent =

A

NaBH4

17
Q

Reaction of carbonyl compound with HCN and propanal

also state it’s purpose?

A

CH3CH2CHO + HCN&raquo_space;> CH3CH2CHOHCN

in the presence of H2SO4/NaCN

PURPOSE IS to increase the length of the carbon chain

18
Q

how is silver mirror formed

A

from the reduction of silver

Ag+(aq) + e-&raquo_space;> Ag(s)

19
Q

Distinguishing carboxylic acids from phenol

A

phenols are not acidic enough to react with the weak base carbonates (sodium carbonate)

but carboxylic acids are, hence reacting with sodium carbonate to produce CO2(g)

20
Q

describe the preparation of acyl chlorides

A

Carboxylic acids + SOCl2&raquo_space;» acyl chloride + SO2(g) + HCL(g)

HCL is misty white fumy gas

21
Q

construct the acyl chloride flow chart

A

Add a pic next time

22
Q

acyl chloride&raquo_space;> primary amide

A

Acyl chloride + NH3&raquo_space;> primary amide +NH4Cl

R-COCl + 2NH3&raquo_space;» R-CONH2 + NH4Cl

23
Q

acyl chloride&raquo_space;> secondary amide

A

R-COCl + 2RNH2&raquo_space;» RCONHR + RNH3+Cl-

24
Q

Reaction of acid anhydrides with alcohol

Draw out the reaction of

2(CH3CO)2O + C6H5OH

A

acid anhydride + alcohol&raquo_space;> Ester + carboxylic acid

2(CH3CO)2O + C6H5OH&raquo_space;> CH3COOC6H5 + CH3COOH

25
Q

Word equation between the reaction of acid anhydride reacting with alcohol

A

Acid anhydride + alcohol&raquo_space;> Ester + carboxylic acid

26
Q

How do you identify between an aldehyde or ketone by melting point?

A
  • impure orange ppt is filtered
  • The solid ppt is the recrystallised to produce a pure crystals
  • The M.P of the purified 2,4 DNPH ppt is measured and compared to the database of melting points

chemistry ocr a a level (35 decks)

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