Carboxylic Acids Flashcards
What is the functional group for carboxylic acid?
COOH
How are carboxylic acids made?
primary alcohols are oxidised into aldehydes
aldehydes are further oxidised into carboxylic acids
How are carboxylic acids made?
primary alcohols are oxidised into aldehydes
aldehydes are further oxidised into carboxylic acids
What is the overall equation for the formation of a carboxylic acid?
alcohol + 2[O] > Carboxylic acid + water
Which carboxylic acids are very soluble?
those with a low molecular mass
this is bc the COOH group forms hydrogen bonding with water
Why are carboxylic acids weak?
only slightly dissociated in water
only partially give their proton
How are carboxylic acids dissociated?
carbonyl grouo (C=O) attracts electrons away from the -OH group
this causes the -OH bond to be weakened so it breaks easily to release a proton and produce a carboxylate anion
What is the equation for dissociation
CH3COOH ⇌ CH3COO- + H+
Why are alcohols not acidic?
the -OH bond doesn’t break easily
Why does the addition of a halogen change a CA acidity?
- halogen is electron withdrawing
- so OH bond is weaker
- thus its a stronger acid
What is the test for carboxylic acids?
Na2CO3 (sodium carbonate)
observation: effervescence
What is the word equation for CA with sodium carbonate?
e.g ethanoic acids
ethanoic acid + sodium carbonate > sodium ethanoate + carbon dioxide + water
What is the equation for CA and sodium carbonate?
e.g methanoic acids ethanoic acid
2COOH + Na2CO3 > 2COO-Na+ + CO2 + H2O
How are esters formed?
esterification
carboxylic acids react with alcohols in the presence of a strong acids
What are the uses of esters
flavourings
perfumes
plasticisers
What catalyst is used in esterification?
Concentrated sulphuric acid (H2SO4)
What is the WORD equation for esterification?
carboxylic acid + alcohol ⇌ ester + water
What is the equation for Esterification?
e.g methanoic acid
CH3CO OH + CH3O H ⇌ CH3COCH3O + H2O
How do you name an ester?
the alky chain is the prefix > e.g methanol is methyl etc
the carboxyl-acid is the suffix and changed from -oic to -oate
What is a functional group isomer?
same molecular formula but different structural formula
How can esters be hydrolysed into carboxylic acids?
using diluted H2SO4 of HCL as a catalyst along with water
reversible so gives low yeild of CA
What is basic hydrolysis?
when an ester is hydrolysed into an alcohol and carboxylic salt when heated with an alkali
What is the equation for the first step of basic hydrolysis?
Add alkali (NaOH)
e.g ethanoic acid
CH3CO|OCH3 + NaO|H > CH3COO-Na+ CH3OH
what is the second step of basic hydrolysis?
add excess acid (dilute H2SO4 or HCl) and carboxylic acid is reformed
CH3COO-Na + HCL > CH3COOH + NaCl
What are triesters?
triglycerides of long chain carboxylic acids (fatty acids) and gylcerol
they occur as fats and oils
What is formed when triglycerides are hydrolysed?
hydrolysed using hot NaOH or KOH
glycerol and sodium/potassium salts of long chain carboxylic acids (carboxylate salts)
What are carboxyate salts used for?
soap
What is biodiesel?
liquid fuel consisting of a mixture of methyl Esters of long chain carboxylic acid from vegetable oil
how do you Hydrolyse fats/oils into biodiesel?
react with a methanol with a strong acid/alkaline as a catalyst
This forms a mixture of methyl Esters
What is bio diesel used for?
Fuel in diesel vehicle vehicles
What are the two functional groups of carboxylic acids?
acyl chlorides and acid anhydrides
What is a acyl chloride!
the -OH group in a carboxylic acid is replaced by a chlorine atom
how do you name an acyl chloride?
suffix = oyl chloride
Ethanolic acid ethanoly chloride
what is the equation for nucleophilic addition elimination?
CH3COCl + XH > CH3COX + HCl
what are the four different nuclear phases that were react with acyl chlorides?
water
alcohol
ammonia
amines
What is the name of the mechanism with acyl chlorides?
Nucleophilic edition elimination
what are the advantages of using acyls to make esters?
no catalyst is needed
purer product
High yield because the reaction is not reversible
what is a limitation of using acyl chlorides?
HCL is toxic and corrosive
how amides formed?
when acyl chlorides react with ammonia
How do you name N-substituted amides?
N and the suffix -anamide
what is an advantage of using acid anhydrides?
cheaper
React less exothermically so the reaction is less violent
Less vulnerable to hydrolysis
HCL is not formed
High yield
what forms acid anhydrides?
Went to carboxylic acid joined together with the elimination of water
how do you name an acid anhydride?
-anhydride replace the -acid suffix
why are acid anhydrides leave groups good?
they activate the adjacent carbonyl group by electron withdrawal
what is a good leaving group?
A stable species which is removed during a chemical reaction
What are the three ways to create carboxylic acids?
- primary alcohols/aldehydes are oxidised by acidified potassium dichromate
- acyl chloride react with water
- acid anhydrides with water
What are the three way to create an Esther?
- carboxylic acid reacting with an alcohol
- acyl chloride with alcohol
- acyl anhydrides with alcohol
