Carboxylic Acids and Esters Flashcards
Microbial Oxidation of Ethanol
Presence of oxygen and acetic acid bacteria:
ethanol + oxygen -> ethanoic acid + water
Chemical Oxidation of Ethanol
Heating with oxidising agent - potassium dichromate (K2Cr2O7) in dilute sulfuric acid
C2H5OH + 2[O] -> CH3COOH + H2O
Color change - orange -> green as K2CrO7 gets reduced
Carboxylic acids functional group
O=C-OH
Carboxylic acid ion charge
-1 (loses the H)
Metal + carb. acid
Metal __oate (aq) + H2(g)
Metal carbonate + carb. acid
Metal __oate + CO2(g) + H2O(l)
What kind of solution is vinegar and what does it contain
aqueous, containing ethanoic acid
Esters functional group
O=C-O
carboxylic acid (l) + alcohol (l)
(esterification)
OH lost from carb. acid
H lost from alcohol
<-> __yl __oate (l) + H2O (l)
^ is an ester
condensation reaction (water formed)
It is a reversible reaction
Displayed formula of ethyl ethanoate
…O
||
C-C-O-C-C
no hydrogen displayed
Structural formula of ethyl ethanoate
CH3COO CH2CH3
carb. \alcohol
Where does H2O come from in esterification
OH - carboxylic acid
H - alcohol
Properties and uses of esters
-Volatile compounds (turns into a vapour easily) with distinctive smells
-Used as food flavourings and in perfumes
(Sweet fruity smell)
Practical: Prepare a sample of an ester (e.g. ethyl ethanoate)
Heat a mixture of ethanoic acid and ethanol (in a water bath)
Add a few drops of concentrated sulfuric acid as reaction catalyst
Ethyl ethanoate is produced
Condensation polymerisation
Dicarboxylic acid + diol
Forms polyester
For every monomer joined, a separate molecule of water is produced
