Chemistry Paper 2 (Essay) ,May/June 2011

Questions:		1	2	3	4	5	6	7	8		Main

General Comments
Weakness/Remedies
Strength

Question 4
(a) (i) What is a functional group? (ii) State the functional group ion each f the following compounds: I. CH3CH2CH(CH3)OH; II. CH3CH2CH2COOH. (b) i) Complete the following equations: O I. CH3C ----- OCH2CH2CH3 + H2O O II. CH3CH2CH2CH2C OCH3 + H2O NaOH, heat (ii) Draw the structure(s) of the product(s) formed in 4(b)(i) above. (c) (i) Write an equation for the preparation of butan-2-ol from butane.(d) (i) Give the reagents required for the following conversions to take place: I. CH2 = CH2 to CH3CH2OH; II. CH3CH2OH to CO3COOH; III. CH3COOH to CH3COOCH2CH3. (e) Consider the following organic structure; CH3 = CHCH = CHCOOH OH (i) State what would be observed when the organic compound is treated with each of the following reagents: I. cold NaHCO3(aq); II. hot solution of I2 in NaOH(aq); III. bromine water (ii) State the functional group responsible for each of the observations in 4(e)(i) above.
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OBSERVATION
This question was not popular. Responses from candidates showed that this section of the syllabus has not been adequately covered or treated. Part (a), most of the responding candidates could not describe what a functional group is but were able to state the functional group in the compounds listed. Part (b), most of the candidates could not give the correct products of the organic reactions and hence could not draw the structures of the products formed. Part (c) was poorly attempted. Most of the candidates could not write the correct equation for the preparation of butan-2-oƖ; from butene. Part (d), was also poorly attempted as most candidates could not give the correct reagents required for the conversion to take place. Part (e), most candidates could not state the correct observations. Instead of stating an effervescence for example, most candidates reported a colourless, odourless gas was evolved while few candidates were able to state that the bromine water was decolourised. The expected answers are: (a)(i) It is an atom or group of (bonded) atoms that is responsible for the Chemical behaviour of an organic compound. ii) I. – OH or hydroxyl group/alkanol II. – C = O/carboxylic/alkanoic OH (b)(i) I. H+, heat CH3COOH + CH3CH2 CH2 OH II. NaOH, heat CH3(CH2)3CH2COONa + CH3 OH (ii) I. H H H H O H C C H C C C OH H OH H H H II. H H H H O H H C C C C C ONa H C O H H H H H H (c) C4H8 + H -HSO4 C4H9HSO4 C4H9 HSO4 + H2O C4H9 HO + H2SO4 Accept CH2 = CHCH2CH3 + H2O H+ CH3CHCH2CH3 OH OR C4H8 + H2O H+ C4H9OH (d) I. Conc. H2SO4/H3PO4 II. acidified KMnO4 /K2Cr207/Na2Cr2O7 III. ethanol Conc H2SO4 (e)(i) I. effervescence occurs II. yellow precipitate III. bromine water decolourised (ii) O I. - C - OH /alkanoic group II. CH3CHOH/CH3 adjacent to CHOH III. C = C / carbon – carbon double bond