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Carboxylic acids Flashcards

1
Q

what functional group does carboxylic acid have?

A

COOH

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2
Q

What is the name of the functional group COOH?

A

carboxyl

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3
Q

are carboxylic acids soluble in water?

A

yes

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4
Q

why are carboxylic acids soluble?

A

due to the hydrogen bonding which can occur between the O-H in the carboxyl group and the O-H on the water molecules

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5
Q

as the carbon chain length increases, what happens to the solubility?

A

it increases

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6
Q

Q. Explain why ethanedioc acid more soluble in water than pentanoic acid?

A

Ethanedioic acid has two –COOH groups so it forms more hydrogen bonds than pentanoic acid.

Pentanoic acid has a longer hydrocarbon chain which cannot form hydrogen bonds with water, only induced dipole-dipole interactions with each other.

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7
Q

what is the boiling point in carboxylic acids?

A

higher boiling points than those of alkanes of a similar size because their O-H group will form hydrogen bonds.

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8
Q

Q. Carboxylic acids are described as organic acids. What does this mean?

A

they contain carbon

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9
Q

Carboxylic acids are also described as weak acids.
What does this mean?

A

They are proton donors and
only partially dissociate into its ions in aqueous solutions

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10
Q

acid + metal, makes?

A

salt + hydrogen

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11
Q

acid + base, makes

A

salt + water

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12
Q

acid + alkali, makes

A

salt + water

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13
Q
A
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14
Q

acid + carbonate, makes

A

salt + carbon dioxide + water

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15
Q

what is a salt?

A

A salt is an acid that has had its hydrogen ion replaced by a metal ion or other positive ion

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16
Q

a base is…

A

a proton (H+) acceptor

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17
Q

an alkali is..

A

a soluble base

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18
Q

how are carboxylic acids formed from 1o alcohols?
Write an equation for the formation of methylpropanoic acid from a suitable alcohol.

A

(CH3)2CHCH2OH + 2[O] → CH3CH(CH3)COOH + H2O
Methylpropan-1-ol

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19
Q

From Aldehydes: Write an equation for the formation of ethanoic acid from a suitable aldehyde.

A

CH3CHO + [O] → CH3COOH
Ethanal

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20
Q

how are nitriles turned into carboxylic acids?

A

The nitrile functional group, CN, can be turned into a carboxylic acid by hydrolysis.

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21
Q

what reagents are needed to turn carboxylic acids from nitrile?

A

dilute hydrochloric acids

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22
Q

what conditions are needed to turn carboxylic acids from nitrile?

A

reflux

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23
Q

what is the general equation for the hydrolysis of the nitrile group?

A

R-CN + HCl +2H2O → R-COOH + NH4Cl

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24
Q

Write an equation for the hydrolysis of ethanenitrile.

A

CH3CN + 2H2O + HCl → CH3COOH + NH4Cl

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25
Q

Write an equation for the hydrolysis of 2-hydroxy-propanenitrile.

A

CH3CH(OH)CN + 2H2O + HCl → CH3CH(OH)COOH + NH4Cl

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26
Q

what functional group does acyl chlorides have?

27
Q

how are acyl chlorides formed from carboxylic acids?

A

Acyl chlorides are formed from carboxylic acids by replacing the OH on the carboxylic acid with a Cl. This can be achieved using sulfur dichloride oxide (thionyl chloride), SOCl2 or phosphorus (V) chloride, PCl5.

28
Q

how are acyl chlorides named?

A

Acyl chlorides are named by replacing the –oic acid with –oyl chloride.

29
Q

how are acyl formed using sulfure dichloride oxide?

A

The sulfur dichloride oxide reacts with carboxylic acids to produce an acyl chloride, sulfur dioxide and hydrogen chloride.

30
Q

Write an equation for the reaction between propanoic acid with sulfur dichloride oxide

A

propanoic acid + sulfur dichloride oxide –> propanoyl chloride + sulfur dioxide+ hydrogen chloride

31
Q

how are acyl chlorides formed from Phosphorus(V) chloride?

A

Phosphorus (V) chloride is a solid which reacts with carboxylic acids in the cold to give steamy acidic fumes of hydrogen chloride. It also produces a liquid mixture of the acyl chloride and a phosphorus compound, phosphorus trichloride oxide (phosphorus oxychloride), POCl3.

32
Q

is acyl chloride or carboxylic acid more reactive, why?

A

An acyl chloride is much more reactive than the carboxylic acid. The reaction is more vigorous and goes to completion. It is not reversible.

33
Q

why must the acyl chloride react be kept dry?

A

The reaction must be kept dry, so that the acyl chloride is not hydrolysed by water.

34
Q

hydrolysis of acyl chlorides - rules keeping dry

A

If acyl chlorides are not kept dry they will readily hydrolyse to form carboxylic acids & misty fumes of hydrogen chloride.

35
Q

what is the general equation for the hydrolysis of acyl chlorides?

A

R-COCl + H2O → R-COOH + HCl

36
Q

Write an equation to show the hydrolysis of ethanoyl chloride, CH3COCl

A

CH3COCl + H2O → CH3COOH + HCl

37
Q

what reaction causes the formation of esters using acyl chlorides?

A

esterification

38
Q

what reagents are needed for the formation of esters using acyl chlorides?

39
Q

what reagents are needed for the formation of esters using acyl chlorides?

A

room temp/dry

40
Q

what products are formed for the formation of esters using acyl chlorides?

A

ester and hydrogen chloride

41
Q

what reagents are needed for the formation of phenyl ester and hydrogen chloride using acyl chlorides?

A

Phenol (Carboxylic acids are not reactive enough to form esters with phenols)

42
Q

what conditions are needed for the formation of phenyl ester and hydrogen chloride using acyl chlorides?

A

room temp/dry

43
Q

what is the functional group of an ester?

44
Q

what are two main uses of esters?

A

Two main uses of esters are for perfumes and flavourings.

45
Q

what is the process of making esters called?

A

They are made by a process called esterification.

46
Q

what is a condensation reaction?

A

A reaction in which two small molecules react together to form a larger molecule with the elimination of water or other small molecule. (e.g. HCl)

47
Q

what type of reaction is esterification?

A

condensation reaction

48
Q

what reagents are needed for the esterification of carboxylic acids with alcohols?

A

carboxylic acid and alcohol

49
Q

what conditions are needed for the esterification of carboxylic acids with alcohols?

A

conc.H2SO4 and reflux

50
Q

what are the products of ethanoic acid + 2-methylpropan-1-ol?

A

2-methylpropylethanoate

51
Q

Name the ester made from ethanol and pentanoic acid:

A

ethyl pentanoate

52
Q

how can esters be hydrolysed?

A

Esters can be hydrolysed (splitting by water) using either acidic or alkaline hydrolysis.

53
Q

what are the reagents needed for acidic hydrolysis?

A

HCl (aqueous)

54
Q

what conditions are needed for acidic hydrolysis?

A

heat and reflux

55
Q

what reaction is acidic hydrolysis?

A

The reaction is exactly the revere of the esterification reversible reaction above.

56
Q

Write an equation for the acid hydrolysis of
methylpropanoate.

A

CH3CH2COOCH3 + H20 ⇌ CH3CH2COOH + CH3OH

57
Q

what is the reagent used for alkaline hydrolysis?

A

aqueous sodium hydroxide

58
Q

what are the conditions used for alkaline hydrolysis?

A

Heat and Reflux

59
Q

what is the alkaline hydrolysis used for?

A

This reaction with hot alkali is used to make soap and is known as saponification. Vegetable and animal fats containing triglycerides (which are esters of carboxylic acids) are hydrolysed into the sodium salt of the carboxylic acid (sodium carboxylate), which can be used as a soap product.

60
Q

what is the equation that shows the alkaline hydrolysis?

A

RCOOCH2R’ + NaOH –> RCOONa + R’CH2OH

61
Q

Write an equation for the alkaline hydrolysis of methylpropanoate?

A

CH3CH2COOCH3 + NaOH –> CH3CH2COONa + CH3OH

62
Q

Write the equation, using structural formulae, for the acid hydrolysis of ethyl butanoate and name the products.

A

CH3CH2CH2COOCH2CH3 + H2O –> CH3CH2CH2COOH + CH3CH2OH
butanoic acid and ethanol

63
Q

Write the equation, using structural formulae, for the alkaline hydrolysis of propyl methanoate and name the products.

A

HCOOCH2CH2CH3 + NaOH –> HCOONa + CH3CH2CH2OH
sodium methanoate & propan-1-ol

chemistry sem 2 (10 decks)

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