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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

A

Equal concentration of enantiomers / (optical) isomers

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2
Q

What is an enantiomer?

A

Non-superimposable mirror image

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3
Q

Explain how a pair of stereoisomers can be distinguished.

A

(Plane) polarised light
Rotated in opposite directions

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4
Q
A
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5
Q

What is plane polarised light?

A

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

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6
Q

What is a chemical property of an optical isomer?

A

4 different groups attached

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7
Q

What are 2 physical properties of an optical isomer?

A

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

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8
Q

How do you draw an optical isomer?

A

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

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9
Q

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

A

nucleophilic addition

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10
Q

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

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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11
Q

Are carboxylic acids strong or weak acids?

A

They are weak so they partially dissociate in water

Forming a carboxylate ion and a H+ ion

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12
Q

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

A

A salt, carbon dioxide and water

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13
Q

Why are carboxylic acids soluble in water?

A

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

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14
Q

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

A

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

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15
Q

What are the reagents and reaction conditions for esterification?

A

alcohol, carboxylic acid and H2SO4 catalyst
(heated)

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16
Q

How are esters named?

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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17
Q

What are the uses of 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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18
Q

Why do esters make good plasticisers?

A

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

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19
Q

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

A

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

(Reverse esterification)

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20
Q

Why is a high temperature required to melt fats?

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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21
Q

Why are oils easier to melt?

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

22
Q

What is formed from the hydrolysis of fats and oils?

A

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

23
Q

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

A

Add HCl

24
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

25
Q

What is the test for an aldehyde?

A

Tollen’s reagent - silver mirror

26
Q

What are aldehydes and ketones?

A

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

27
Q

What are some hazards of KCN?

A

Toxic and flammable

28
Q

What are some safety precautions for KCN?

A

Fume cupboard and water bath

29
Q

What is formed when oxidising a primary alcohol?

A

Primary alcohol —> aldehyde —> carboxylic acid

30
Q

What happens when you oxidise a secondary alcohol?

A

Secondary alcohol —> ketone

31
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

32
Q

Tollen’s Reagent

A

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

33
Q

Can tertiary alcohols be oxidised?

A

no

34
Q

Why are carbonyls polar?

A

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

35
Q

Why are carbonyls susceptible to nucleophiles ?

A

Trigonal planar shape of the group

36
Q

Why are shorter chain carbonyls soluble in water?

A

They can form h bonds with water molecules

37
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

38
Q

Which 3 types of reaction do carbonyls undergo?

A
  1. Addition
  2. Nucleophilic addition
  3. Redox
39
Q

Example Q

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

A

CH3OH + CH2H5COOH —> CH3CH2COOCH3 + H2O

40
Q

Acylation

A

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

41
Q

what is an Addition-Elimination reaction

A

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

42
Q

What are the 3 acid derivatives

A

Esters
Acyl chlorides
Acid anhydrides

43
Q

What are acyl chlorides?

A

Have the functional group CoCl, suffix is -oyl

44
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

45
Q

What are acid anhydrides?

A

Two identical carboxylic acid molecules, joined via oxygen

46
Q

What does an acid anhydride and water produce?

A

2 ethanoic acids

47
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

48
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

49
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

50
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 (33 decks)

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