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Chem Unit 4 > 4.5 Carboxylic Acids > Flashcards

4.5 Carboxylic Acids Flashcards

1
Q

order the relative acidities of carboxylic acids, water, phenols and alcohols

A

In order of decreasing acidity: carboxylic acids, phenols, water, alcohols

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2
Q

Type of reaction carried out when an alcohol reacts to form a carboxylic acid

A

oxidation

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3
Q

Intermediate product formed suring the oxidation of an alcohol to form a carboxylic acid?

A

The alcohol is oxidised to an aldehyde, this is the intermediate product which then undergoes further oxidation to form a carboxylic acid

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4
Q

Chemical eqn for the oxidation of ethanol to form ethanoic acid?

A

Two reactions take place consecutively:
CH3CH2OH + [O] -> CH3CHO (aldehyde intermediate) + H2O
CH3CHO + [O] -> CH3COOH
overall: CH3CH2OH + 2[O] -> CH3COOH + H2O

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5
Q

What reaction conditions req to ensure complete oxidation of the clocohol to carboxylic acid?

A

Excess oxidising agent (acidified potassium dichromate (VI)) needs to be added to the alcohol and it must be heated under reflux

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6
Q

Most common oxidising agent used for the oxidation of alchols?

A

Acidified potassium dichromate (VI)

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7
Q

What type of alcohol will produce carboxylic acids when oxidised??

A

Primary alcohols

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8
Q

What is the reducing agent used to reduce carboxylic acids to alcohols?

A

LiAlH4

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9
Q

Why is NaBH4 used to reduce aldehydes and ketones but not carboxylic acids?

A

NaBH4 is a safer reducing agent than LiAlH4 so is preferred when reducing aldehydes and ketones but NaBH4 cannot be used to reduce carboxylic acids because it is not reactive enough

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10
Q

Chemical eqn for the reduction of propanoic acid, what is the name of the product formed?

A

CH3CH2COOH + 4[H] -> CH3CH2CH2OH + H2O porpan-1-ol

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11
Q

what reagents are req to oxidise methylbenzene to benzoic acid?

A

Alkaline potassium manganate (VII) is fist added to methylbenzene, once a dark brown ppt forms the mixture is acidified with dilute sulfuric acid

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12
Q

Methylbenzene forms benzoic acid under oxidation, what does propylbenzene form when it undergoes oxidation?

A

Benzoic acid reargless of the side chain length all side chains are oxidised to a -COOH group.

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13
Q

Decarboxylation??

A

Decarboxylation is the process by which the -COOH functional group of a carboxylic acid or -COO-Na+ group of a carboxylate salt is removed from the molecule and replaced with a hydrogen atom

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14
Q

common reagent used for decarboxylation?

A

soda lime (contain NaOH)

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15
Q

Chemical equation for the rctn between sodium ethanoate and soda lime?

A

CH3COO-Na+ + NaOH -> CH4 + Na2CO3

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16
Q

Chemical eqn for the rctn between benzoic acid and soda lime?

A

C6H5COOH + 2NaOH -> C6H6(benzene ring) + Na2CO3 + H2O

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17
Q

What os formed when an alcohol reacts with a carboxylic acid?

A

An ester

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18
Q

Functional group of an ester

A

-COO-

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19
Q

Condition an catalyst required for an esterification reaction

A

The alcohol and carboxylic acid must be heated in the presence of a strong acid catalyst e.g. conc H2SO4

20
Q

Chem eqn rctn bet ethanoic acid and ethanol??

A

CH3COOH + CH3CH2OH -> CH3COOCH2CH3 +H2O

21
Q

Ester formed in rctn bet butanoic acid and propanol??

A

Propyl butanoate

22
Q

Identifying properties of esters?

A

Sweet smellign used in flavourings and perfumes, low boiling points making them good solvents for other polar molecules

23
Q

What is used as a catalyst in esterification reactions?

A

Conc sulfuric acid

24
Q

Why is hydrogen chloride sometimes a preferred catalyst for esterification?

A

Hydrogen chloride gives a better yield since no alkene products are formed

25
Q

3 possible reagents used to prod an acyl chloride from a carboxylic acid

A

Phosphorus(V) chloride PCL5
Phosphorus(III) chloride PCl3
Sulfur dichloride oxide SOCl2

26
Q

Chem eqn for rctn bet ethanoic acid and phosphorus(V) chloride?

A

CH3COOH + PCl5 -> CH3COCl + POCl3 + HCl

27
Q

Chemical eqn for rctn bet propanoic acid and phosphorus(III) chloride

A

3CH3CH2COOH + PCl3 -> 3CH3CH2COCl + H3PO3

28
Q

Chem eqn for rctn bet ethanoic acid and sulfur dichloride oxide?

A

CH3COOH + SOCl2 -> CH3COCl + SO2 + HCl

29
Q

Why is SOCl2 the preferred reagent when making acid chlorides?

A

In rctn with SOCl2 byproducts are gaseous so it is easier to obtain acid chloride, isolation of acid chloride is more difficult when using PCl3 or PCl5

30
Q

Type of rctn in which esters and acid chlorides react to form carboxylic acids

A

Hydrolysis (rctn substance split up by water)

31
Q

What are the different setups req for acid hydrolysis of an ester and a base hydrolysis?

A

Acid hydrolysis: Ester must be refluxed with a dilute acid HCl/ H2SO4
Base hydrolysis: Ester must be refluxed with dilute alkali NaOH

32
Q

Products formed when ethyl ethanoate undergoes acid hydrolysis and base hydrolysis

A

Acid hydrolysis: Ethanoic acid and ethanol
Base hydrolysis: Ethanoate ion and ethanol

33
Q

How does hydrolysis of acid chlorides compare with hydrolysis of esters

A

Hydrolysis of acid chlorides is much more rapid than the hydrolysis of esters, acid chlorides react vigorously with cold water

34
Q

Chem eqn for rctn of ethanoyl chloride with water

A

CH3COCl + H2O -> H3CCOOH + HCl

35
Q

How is an amode made from a carboxylic acid?

A

First ammonium carbonate added to excess carboxylic acid until ammonium salt formed which is heated to undergo dehydration and prod an amide

36
Q

How is a nitril made from an amide?

A

A nitrile prod is an amide undergoes dehydration by heating with Phosphorous(V) oxide

37
Q

Chem eqn for formation of ammonium salt when ethanoic acid reacts with ammonium carbonate?

A

2CH3COOH + (NH4)2CO3 -> 2CH3COONH4 + H2O + CO2

38
Q

Give the reactants and conditions required for the formation of a hydroxynitrile from an aldehyde/ketone

A

Potassium or sidum cyanide is added to sulfuric acid to produce hydrogen cyanide, temperature 20C

39
Q

Why is hydrogen cyanide not added directly to an aldehyde/ketone for a nucleophilic addition reaction?

A

Hydrogen cyanide is a toxic gas

40
Q

Draw and name mechanism for formation of 2-hydroxypropanenitrile from ethanal and hydrogen cyanide

A

Nucleophilic addition
polarity in c doblue bond o C from hctriple bond n attacks intermediate -two lone paris on O attacks +H ctriple bond n attaches then prod hydroxynitrile

41
Q

What is produced when a halogenoalkane reacts with ethanolic potassium cyanide?

A

a nitrile

42
Q

Name of product formed when 2-bromopropane reacts with ethanolic potassium cyanide

A

2-methylpropane

43
Q

Describe the stages in hydrolysis of nitriles

A

First nitriles react with water to produce amides which undergo further hydrolysis and react with water to form either a carboxylic acid or a carboxylate salt depending on reaction conditions

43
Q

How do the reactants and products of base hydrolysis of nitriles compare to those of acid hydrolysis of nitriles?

A

acid hydrolysis: reactants: dilute HCl products: carboxylic acid and ammonium chloride(NH4Cl)
base hydrolysis: reactants: dilute sodium hydroxide products: sodium carboxylate salt and ammonia(NH3)

44
Q

Reducing agent used in reduction of nitriles to amines?

A

LiAlH4

45
Q

Chemical eqn for reduction of propanenitrile to propylamine?

A

CH3CH2CN + 4[H] -> CH3CH2CH2NH2

Chem Unit 4 (8 decks)

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