The formulae of four organic compounds are given below:
A - C 2 H 4
B - CH 3 COOH
C - C 2 H 5 OH
D - C 2 H 6
(i) Which one of these compounds A, B, C or D is a saturated hydrocarbon?
(ii) Identify the organic acid and give its structural formula.
(iii) Which of the above compounds when heated at 443K in the presence of concentrated H 2 SO 4 forms ethene as the major product? What is the role played by concentrated H 2 SO 4 in this reaction? Also, write the chemical equation involved.
(iv) Give a chemical equation when B and C react with each other in presence of concentrated H 2 SO 4 . Name the major product formed and mention one of its important use.
A saturated hydrocarbon is a compound containing only carbon and hydrogen atoms and in which no double or triple bonds are present between any 2 carbon atoms.
Checking all the options
- C 2 H 4 has a general formula of alkene (C n H 2n ), which means it has a double bond and so is unsaturated .
- CH 3 COOH and C 2 H 5 OH are not hydrocarbons because along with carbon and hydrogen atoms, oxygen is also present.
- C 2 H 6 has a general formula of alkane (C n H 2n+2 ), which means it is a saturated hydrocarbon.
Therefore, D is a hydrocarbon.
Organic acids are compounds which contain a carboxyl functional group(-COOH).
Of these 4 compounds, compound B ie., CH 3 COOH (acetic acid) is the organic acid as it contains the carboxyl functional group.
Its structure is as follows:
(iii) An alcohol with 2 carbon atoms , when heated at 443K in the presence of conc H 2 SO 4 gives ethene as the main product.
Compound C i.e. C 2 H 5 OH(ethanol) is an alcohol and has 2 carbon atoms.
So, when concentrated H 2 SO 4 is added to it, a dehydration reaction takes place where one H 2 O molecule is removed and ethene is formed.
The chemical reaction that takes place is:
Reaction of Ethanol with concentrated H 2 SO 4
Concentrated H 2 SO 4 here plays the role of dehydrating agent and removes water from alcohol.
(iv) Compound B is acetic acid and compound C is ethanol.
When an acid reacts with an alcohol , an esterification reaction takes place.
Reaction of acetic acid with ethanol: