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Chemistry Module 6 > 6.1.3 Carboxylic Acids And Esters > Flashcards

6.1.3 Carboxylic Acids And Esters Flashcards

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1
Q

carboxylic acids acidity

A

weak acids
only partially dissociate
can displace carbon dioxide from carbonates

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2
Q

carboxylic acids solubility in water

A

smaller (up to C4) dissolve in water in all proportions but after this the solubility rapidly reduces
dissolve as they can hydrogen bond to the water molecules

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3
Q

delocalisation of a carboxylic acid

A

stabilised by delocalisation, makes dissociation more likely
delocalised ion has equal C-O bond lengths, if delocalisation didn’t occur then C=O is shorter than C-O
pi charge cloud has delocalised and spread out, makes ion more stable and more likely to form

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4
Q

explain the drawing of the delocalisation of a carboxylic acid

A

draw normal carboxylic acid
then break the double bond C=O and lose the H on OH
draw a dotted c shaped curve with a - inside of a small circle

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5
Q

factors that affect strength of a carboxylic acid

A

chain length

electronegativity

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6
Q

effect of chain length on the strength of a carboxylic acid

A 
decreases the acidity 
alkyl groups are electron donating 
pushes the electron density on to the COO- ion 
makes it more negative and less stable 
makes the acid less strong
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7
Q

effect of electronegativity on the strength of a carboxylic acid

A

more electronegative atom added then the stronger the acidity of the acid
electronegative chlorine withdraw electron density from the COO- ion
makes it less negative and more stable
makes the acid more strong

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8
Q

what reactions can carboxylic acids also take part in

A 
acid + metal -> salt + hydrogen
acid + base -> salt + water 
acid + alkali -> salt + water 
acid + carbonate -> salt + water + CO2
acid + ammonia -> ammonium salt
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9
Q

example of a functional group test for a carboxylic acid

A

effervescence caused by the production of CO2 with carboxylic acids with solid Na2CO3 or aqueous NaHCO3

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10
Q

oxidation of methanoic acid

A

forms carbonic acid H2CO3

which can decompose to give CO2

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11
Q

why can methanoic acid be oxidised using an oxidising agent

A

as its structure effectively has an aldehyde group

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12
Q

esterification

A

carboxylic acids react with alcohols in the presence of a strong sulfuric acid catalyst to form esters and water

carboxylic acid + alcohol (reversible with H+) ester + water

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13
Q

naming an ester

A

2 parts to their name
name them right to left
bit ending in -yl comes from alcohol that has formed it, next to the single-bonded oxygen
bit ending in -anoate comes from the carboxylic acid and includes the C in C=O bond

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14
Q

conditions of esterification

A

requires a strong sulfuric acid catalyst
reversible reaction
quite a slow reaction and needs heating under reflux for several hours or days
low yields are achieved

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15
Q

esterification using acid anhydrides

A 
acid anhydride -> water 
reagent: alcohol 
conditions: room temperature 
NOT REVERSIBLE
(RCO)2O + CH3CH2OH -> RCO2CH2CH3 + RCO2H

React with alcohols to form esters as the main product and a carboxylate salt as a side product

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16
Q

acid anhydrides

A

more reactive than carboxylic acids
not reversible
higher yield achieved

17
Q

hydrolysis of esters reagents

A

acid reagents- dilute HCl

sodium hydroxide reagents- dilute sodium hydroxide

18
Q

hydrolysis of esters with acid reagents

A 
dilute HCl 
heat under reflux 
reversible reaction 
forms a carboxylic acid and an alcohol 
not a good yield
19
Q

hydrolysis of esters with sodium hydroxide reagents

A

dilute sodium hydroxide NaOH
heat under reflux
reaction goes to completion
forms carboxylate salt and alcohol

salt is the anion of the carboxylic acid
anion is resistant to attack by weak nucleophiles such as alcohols so the reaction isn’t reversible

20
Q

acyl chlorides reactivity, explain

A

much more reactive than carboxylic acids
Cl group is classed as a good leaving group (to do with less effective delocalisation), makes acyl chlorides much more reactive than carboxylic acids and esters

21
Q

formation of acyl chlorides from a carboxylic acid

A

carboxylic acid -> acyl chloride
reagent: SOCl2
conditions: room temperature
forms acyl chloride, SO2 + HCl

CH3COOH + SOCl2 -> CH3COCl + SO2 + HCl

22
Q

what is SOCl2

A

sulfur dichloride oxide (thionyl chloride)

it is a liquid

23
Q

what do acyl chlorides react with

A 
water 
alcohol 
ammonia
primary amines 
phenol
24
Q

acyl chlorides reaction with water

A

acyl chloride -> carboxylic acid

reagent: water
conditions: room temperature
observation: steamy white fumes of HCl are given off

example:
RCOCl (l) + H2O -> RCO2H + HCl (g)

25
Q

acyl chlorides reaction with alcohol

A

acyl chloride -> ester and hcl
reagent: alcohol
conditions: room temperature
observation: steamy white fumes of HCl are given off
(better to make esters this way than with carboxylic acid as reaction isn’t reversible and is much quicker)

example:
RCOCl (l) + CH3CH2OH -> RCO2CH2CH3 + HCl (g)

26
Q

acyl chlorides reaction with ammonia

A

acyl chloride -> primary amide

reagent: ammonia
conditions: room temperature
observation: white smoke off NH4Cl is given off

example:
RCOCl (l) + 2NH3 -> RCONH2 + NH4Cl (s)

27
Q

acyl chlorides reaction with primary amines

A

acyl chloride -> secondary amine

reagent: primary amine
conditions: room temperature

examples:
RCOCl + 2 CH3NH2 -> RCONHCH3 + CH3NH3+Cl-

28
Q

acyl chlorides reaction with phenol

A

acyl chloride -> ester

reagent: phenol
conditions: room temperature
observation: steamy white fumes off HCl are given off

example:
RCOCl (l) + C6H5OH -> RCO2C6H5 + HCl (g)

29
Q

phenols reactivity with carboxylic acids vs acyl chlorides

A

don’t easily form esters with carboxylic acids but do with acyl chlorides

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