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Chemistry > Carbonyl groups > Flashcards

Carbonyl groups Flashcards

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1
Q

Give the meaning of the term racemic mixture

7.2 racemic mixture

A

Equal concentration of enantiomers / (optical) isomers

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2
Q

What is an enantiomer?

7.2 racemic mixture

A

Non-superimposable mirror image

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3
Q

Explain how a pair of stereoisomers can be distinguished.

7.2 racemic mixture

A

(Plane) polarised light
Rotated in opposite directions

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4
Q

What is plane polarised light?

7.2 racemic mixture

A

If passed through a polarising filter, the light vibrates in the same plane

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5
Q

What is a chemical property of an optical isomer?

7.1 optical isomerism

A

4 different groups attached

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6
Q

What are 2 physical properties of an optical isomer?

7.1 optical isomerism

A

Can arrange them in different ways to form 2 different molecules, and cannot be superimposed

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7
Q

How do you draw an optical isomer?

7.1 optical isomerism

A

Locate chiral centre, draw an enantiomer in a tetrahedral shape, and draw its mirror image

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8
Q

Why would testing the optical activity of a racemic mixture not be useful

7.2 racemic mixture

A

A racemic mixture contains equal concentrations of enantiomers.
Each enantiomer will rotate the plane of polarised light by an equal but opposite amount
There would be no net change in the plane of polarised light.

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9
Q

Name the type of reaction between an aldehyde or ketone with hydrogen cyanide

8.1 Aldehydes and ketones

A

nucleophilic addition

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10
Q

Are carboxylic acids strong or weak acids?

8.2 Carboxylic acids and esters

A

They are weak so they partially dissociate in water

Forming a carboxylate ion and a H+ ion

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11
Q

What is formed when a carboxylic acid reacts with a carbonate?

8.2 Carboxylic acids and esters

A

A salt, carbon dioxide and water

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12
Q

Why are carboxylic acids soluble in water?

8.2 Carboxylic acids and esters

A

Polar C=O and O-H bonds allowing them to hydrogen bond.

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13
Q

What happens to the solubility of a carboxylic acid as the chain length increases?

8.2 Carboxylic acids and esters

A

solubility decreases, because the size of the hydrophobic non-polar part of the molecule increases

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14
Q

What are the reagents and reaction conditions for esterification?

8.2 Carboxylic acids and esters

A

alcohol, carboxylic acid and H2SO4 catalyst
(heated)

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15
Q

How are esters named?

8.2 Carboxylic acids and esters

A

The prefix of the alcohol with -yl as a suffix and the prefix of the acid with-oate as the suffix. For example, ethanol and ethanoic acid would react to form ethyl ethanoate

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16
Q

What are the uses of esters?

8.2 Carboxylic acids and esters

A
  • Perfumes and flavourings
  • esters make good solvents in glues and prinking inks because they are polar so dissolve things easily, and evaporate easily from mixtures
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17
Q

Why do esters make good plasticisers?

8.2 Carboxylic acids and esters

A

Make things more flexible, molecules escape and plastic becomes brittle and stiff

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18
Q

What are the reaction conditions and product of the acid hydrolysis of an ester?

8.2 Carboxylic acids and esters

A

Reaction conditions - HCl catalyst, H2O, heat
Forms - carboxylic acid and an alcohol

(Reverse esterification)

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19
Q

Why is a high temperature required to melt fats?

8.2 Carboxylic acids and esters

A

They fit neatly together, increasing van der Waals forces between then and the energy required to overcome forces and melt them
- usually solids

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20
Q

Why are oils easier to melt?

8.2 Carboxylic acids and esters

A

Double bonds mean chains are bent and don’t pack together, decreasing the effect of van der Waals and requiring less energy
- usually liquid

21
Q

What is formed from the hydrolysis of fats and oils?

8.2 Carboxylic acids and esters

A

React with sodium hydroxide to form a carboxylate ion (sodium salt, or soap) and an alcohol (glycerol)

22
Q

How do you reverse the effects of hydrolysis of fats and oils?

A

Add HCl

23
Q

How do you get biodiesel from vegetable oils?

A

React with methanol using strong alkali to get a mixture of methyl esters of long chain fatty acids

24
Q

What is the test for an aldehyde?

A

Tollen’s reagent - silver mirror

25
Q

What are aldehydes and ketones?

A

Carbonyl compounds, carbon group on end in aldehydes and in the middle in ketones

26
Q

What are some hazards of KCN?

A

Toxic and flammable

27
Q

What are some safety precautions for KCN?

A

Fume cupboard and water bath

28
Q

What is formed when oxidising a primary alcohol?

A

Primary alcohol —> aldehyde —> carboxylic acid

29
Q

What happens when you oxidise a secondary alcohol?

A

Secondary alcohol —> ketone

30
Q

Fehling’s Solution

A

A solution made of two different solutions, A and B. A contains Cu2+ ions and B contains a complexing agent.
Upon reaction, copper forms along with a precipitate of copper(I) oxide

31
Q

Tollen’s Reagent

A

A solution containing the complex ion [Ag(NH3)2]+.
Upon reaction, a silver precipitate forms along with ammonia

32
Q

Can tertiary alcohols be oxidised?

A

no

33
Q

Why are carbonyls polar?

A

The polarity of the C=O bond makes them polar molecules

34
Q

Why are carbonyls susceptible to nucleophiles ?

A

Trigonal planar shape of the group

35
Q

Why are shorter chain carbonyls soluble in water?

A

They can form h bonds with water molecules

36
Q

Why are longer chain carbonyls not soluble in water?

A

As the chains become longer, there is a greater percentage of non-polar molecule

37
Q

Which 3 types of reaction do carbonyls undergo?

A
  1. Addition
  2. Nucleophilic addition
  3. Redox
38
Q

Example Q

Write an equation for the formation of methyl propanoate, CHCH2COOCH3, from methanol and propanoic acid.

A

CH3OH + CH2H5COOH —> CH3CH2COOCH3 + H2O

39
Q

Acylation

A

The name for the formation of an ester, without needing a mechanism

40
Q

what is an Addition-Elimination reaction

A

The name of the mechanism for the formation of an ester from a acyl chloride

41
Q

What are the 3 acid derivatives

A

Esters
Acyl chlorides
Acid anhydrides

42
Q

What are acyl chlorides?

A

Have the functional group CoCl, suffix is -oyl

43
Q

What is given off when acyl chlorides are reacted with water?

A

Cl is substituted by oxygen or nitrogen and misty fumes of hydrogen chloride are given off and ethanoic acid

44
Q

What are acid anhydrides?

A

Two identical carboxylic acid molecules, joined via oxygen

45
Q

What does an acid anhydride and water produce?

A

2 ethanoic acids

46
Q

How is aspirin made?

A

Made by reacting salicylic acid with either ethanoic anhydride or ethanoyl chloride to form the ester, ethanoic acid is made too

47
Q

Why is ethanoic anhydride usually used?

A

It is cheaper, safer as less corrosive, reacts more slowly and doesn’t produce dangerous hydrogen chloride fumes

48
Q

Why is separation used in the purification of organic compounds?

A

To remove any impurities that do dissolve in water, such as salts or water soluble organic compounds

49
Q

How do you isolate the pure product?

A

Organic layer is usually less dense so should float, with impurities dissolved in lower layer which can be drained off

Chemistry (32 decks)

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