NJC Polymer Part 2 Tutorial Answer

Polymers (Part 2) – Reactions of Functional Groups - Tutorial Alkanes 1 X and Y have a molecular formula of C4H9Br. Both X and Y can be formed from butane by the following reaction. 3 2 2 3CH CH CH CH ⎯⎯ → +XY (a) State the type of reaction undergone in the above reaction. Substitution (b) Suggest reagents and conditions necessary for the above reaction. Limited Br2, UV (c) Suggest the structural formula of X and Y. Structure of X: Structure of Y: X and Y are interchangeable 2 The complete combustion for alkane to produce carbon dioxide and water is an important exothermic reaction. Which line on the graph shows the relationship between the number of carbon atoms in the alkane and the number of moles of oxygen gas needed for complete combustion of the alkane? Ans : B CxHy + (x + y 4) ⎯→ xCO2 + y 2 H2O As number of carbon (x) increases, number of O2 required for combustion increases proportionately A B C D number of moles of oxygen gas 1 number of carbon atoms in alkane

Alkenes 3 One of the four isomers of C4H8 is shown below: A H2C=C (a) Draw the other 3 isomers of C4H8. cis trans (b) State which isomers are cis-trans isomers. 4 Limonene occurs in oil of lemons and is used to flavour citrus drinks. CH3 CH3 CH2 Limonene Give the structural formulae of the organic products, when limonene reacts with (a) H2(g) Reduction of alkene C=C to alkane (each C of C=C gain 1 H) (b) Describe a simple chemical test by which you could distinguish the following pairs of compounds. State the observation for the test and write equation for the reaction. Add Br2 in CCl4 (inert organic solvent). Orange red Br2 is decolourised for limonene, but not for . Equation: CH3 CH3 CH2 + 2 Br2 CH3 CH3 CH2Br Br Br Br H CH2CH3 Limonene and

Halogenoalkanes 5 The following reaction scheme shows the various reactions which bromopropane undergoes. I II CH3CH2=CH2 CH3CH2CH2Br CH3CH2CH2OH (i) State the type of reactions for steps I and II. Step I : Elimination Step II : Substitution (ii) State the reagent and condition for steps I and II. Step I : NaOH (or KOH) in ethanol, heat Step II : NaOH (or KOH) (aq), heat Alcohol 6 (i) Suggest the structural formula of the product of the following reactions and balance the equations. (ii) State the type of reaction undergone in each case. (a) OR Elimination (b) Oxidation (c) Combustion

7 Suggest the intermediates and products formed during the following reactions of 1-bromobutane. • reaction with aqueous NaOH, heat, followed by acidified KMnO 4, heat under reflux. • reaction with NaOH in ethanol, heat, followed by Br 2 in CCl4. C CH H H C H H C H H Br H H NaOH(aq) heat C CH H H C H H C H H OH H H Acidified KMnO4 heat C CH H H C H H C H H OH O C CH H H C H H C H H H Br H NaOHin ethanol heat C CH H H C H H C H H H Br2 in CCl4 C CH H H C H H C H Br H Br H Substitution Oxidation Elimination Addition Aldehyde and Ketone 8 Compound X has the following structure: CH3CH=CHCH2CHO (a) Name the functional groups present in X. Alkene (C=C) and aldehyde (CHO, ) (b) Identify the type of stereoisomerism exhibited by X and draw diagrams to illustrate this isomerism exhibited. cis-trans isomerism (must show trigonal planar around each C of C=C) C C CH3 CH2CHO HH C C CH3 CH2CHO H H cis trans (c) Draw the structural formula of the organic products formed when compound X reacts with the following reagents separately and state the type of reaction involved: (i) acidfied K2Cr2O7, heat under reflux Oxidation of aldehyde to carboxylic acid C CH H H C H C H C H H H O C CH H H C H C H C H H OH O (ii) H2, in the presence of catalyst, heat Reduction of alkene to alkane and reduction of aldehyde to primary alcohol C CH H H C H C H C H H H O C CH H H C H C H C H H H H OH H H

(iii) LiAlH4, dry ether Reduction of aldehyde to primary alcohol C CH H H C H C H C H H H O C CH H H C H C H C H H H H OH (iv) NaBH4, methanol Reduction of aldehyde to primary alcohol C CH H H C H C H C H H H O C CH H H C H C H C H H H H OH Carboxylic Acid 9 Draw the structure of the organic product(s) that is likely to be formed when a compound, with the formula as given below, reacts, if at all, with the following reagents. State the type(s) of reaction undergone (if any) for each reagent used. (a) aqueous NaOH Acid-base reaction (carboxylic acid is acidic) (b) K2Cr2O7(aq), H2SO4 (aq), heat under reflux Oxidation (primary alcohol oxidized to carboxylic acid)

(c) CH3CH2OH, a few drops of conc. H2SO4, heat under reflux Condensation (carboxylic acid with alcohol to form ester) (d) CH3NH2, in the presence of DCC Condensation (carboxylic acid with alcohol to form ester) Ester and Amide 10 There are four ester isomers with the molecular formula C4H8O2. (a) Give the structural formulae of all these isomers. C OH O C C H H C H H H H H C OH O C C H CH3 H H H C OC O C C H H H H HH H H C OC O C H H H C H H H H H (b) For each of the isomer, state the carboxylic acid and alcohol from which the ester is formed. C OH O C C H H C H H H H H CH O OH C C H H C H H H H H HO+ C OH O C C H CH3 H H H CH O OH C C H CH3 H H H HO+

C OC O C C H H H H HH H H CC O OHH H H C C H H H H HO H + C OC O C H H H C H H H H H CC O OHC H H H H H C H H HO H + 11 Give the products for each of the following reactions. (a) CH3CH2CO2CH3, HCl(aq), heat Type of reaction: Acid hydrolysis (b) CH3CO2CH2CH3, NaOH(aq), heat Type of reaction: Alkaline hydrolysis (c) CH3CH2CONH2, HCl(aq), heat Type of reaction: Acid hydrolysis (d) CH3CH2CONHCH3, NaOH(aq), heat Type of reaction: Alkaline hydrolysis 12 Suggest the reagent and condition to form the following organic product from the given starting organic molecule. NH H , DCC