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Chemistry Module 1 > Carboxylic acids > Flashcards

Carboxylic acids Flashcards

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1
Q

Whats the general formula for a carboxylic acid

A

CnH2nO2

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2
Q

What is the functional group

A

COOH

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3
Q

How are they named?

A

either Alkaneoic, Alkeneoic acids

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4
Q

What are some properties of carboxylic acids?

A
  1. Sharp, irritating odour
  2. Short chain carboxylic are liquids and soluble, OH = Hydrogen bonding
  3. Weak acids, only partially ionised
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5
Q

What are the 3 methods of forming carboxylic acids?

A
  1. mild oxidation of primary alcohols and aldehydes
  2. hydrolysis of esters
  3. hydrolysis of nitriles
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6
Q

How does the mild oxidation of a primary alcohol work?

A

Mixture heated under reflux with acidified potassium dichromate (VI) solution

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7
Q

What are esters hydrolysed to?

A

Esters can be hydrolysed to form the carboxylic acid or its salt and the alcohol from which the ester was formed.

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8
Q

What is acid catalysed hydrolysis of an ester?

A

It produces the carboxylic acid and the alcohol. Esters should be heated under reflux with dilute HCl

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9
Q

Draw the acid catalysed hydrolysis of methyl propanoate

A

in book

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10
Q

What is base catalysed hydrolysis of an ester

A

Produces a salt of the carboxylic acid and an alcohol. The ester should be heated under reflux with NaOH solution

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11
Q

Draw the base catalysed hydrolysis of ethyl methanoate and what is special about it? show the two steps and the overall eqn

A

in book
It occurs in two steps, the ester is hydrolysed by water in the presence of the alkali, and then the base reacts with the carboxylic acid to form the salt
Step 1:CH3COOCH3 + H2O→CH3COOH + CH3OH
Step 2: CH3COOH + NaOH → CH3COONa + H2O

Overall equation:
CH3COOCH3 + NaOH → CH3COONa + CH3OH

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12
Q

How are nitriles hydrolysed to produce a carboxylic acid

A
  1. 1st stage is the hydrolysis of the nitrile to form an amide
  2. Next, formation of the acid with the removal of ammonia
  3. Acid hydrolysed - Carboxylic acid and ammonium salt of the acid
  4. Base catalysed - salt of the carboxylic and ammonia
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13
Q

Show the acid catalysed hydrolysis of Ethanenitrile

A

in book

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14
Q

Show the base catalysed hydrolysis of Ethannitrile

A

in book

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15
Q

Draw out the diagram of acid and base catalysed hydrolysis

A

in book

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16
Q

What are the three reactions that occur with carboxylic acids?

A
  1. Reactions with the OH group
  2. Reactions as a weak acid
  3. Reduction reactions
17
Q

What are the 2 reactions with the OH group? and give an example for each

  1. With ethanoic acid
  2. With propanoic acid and ethanol
A
  1. With PCl5 to form the carboxylic acid chloride, POCl3 (Phosphorus oxychloride) and HCl
  2. Esterification, forms Ethyl propanoate
18
Q

What are the reactions as a weak acid?

A
  1. With Sodium Carbonate
  2. With Sodium hydroxide
  3. With ammonia
19
Q

Show the eqn for the reaction of ethanoic acid with sodium carbonate, what are the observations and

A

2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O

Bubbles of gas, solid sodium carbonate disappears.

20
Q

Show the eqn for the reaction of propanoic acid and sodium hydroxide, what are the observations?

A

CH3CH2COOH + NaOH → CH3CH2COONa + H2O

colourless solution, heat given off

21
Q

Show the eqn for the reaction between ammonia and ethanoic acid

A

CH3COOH + NH3 → CH3COONH4

heat released

22
Q

What happens when excess reactant is used?

A

All the functional groups react if it was a di/tribasic acid

23
Q

What is the formula of Oxalic acid and Citric acid

A

HOOC-COOH - Oxalic acid (ethandioic acid)

in book for citric acid (2-hydroxypropane-1,2,3-tricarboxylic acid)

24
Q

Draw the reaction of Magnesium carbonate and Oxalic acid

A

in book

25
Q

How is the reduction of a carboxylic acid carried out

A

Carboxylic acids are reduced to aldehydes and then to primary alcohols, The reduction is carried out by treating the carboxylic acid with lithium tetrahydridoaluminate (Lithal) under reflux in dry ether. Aldehyde is distilled off and prolonged refluxing = primary alcohol

26
Q

How do you prepare a carboxylic acid from a primary alcohol?

A
  1. Add water and concentrated sulfuric acid to a pear shaped flask
  2. Swirl and cool the flask
  3. Add potassium dichromate (VI) solution
  4. Add antibump granules
  5. Add the alcohol slowly
  6. Heat the mixture under reflux
  7. Distill off the acid

Chemistry Module 1 (10 decks)

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