HCI_H2_CHEM_P3 Prelim

This document consists of 14 printed pages. HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 10S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 3 Free Response Candidates answer on separate paper Additional Materials: Answer Paper Data Booklet 9647/03 13 September 2011 2 hours INSTRUCTIONS TO CANDIDATES Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. Begin each question on a new piece of paper. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together. Write down the question numbers for the questions that you have attempted on the cover page provided.

2 © Hwa Chong Institution 2011 9647 / 03 / JC2 Prelim 2011 Answer any four questions. 1 (a) The primary ingredient of a shampoo is a surfactant. A surfactant is an amphiphilic molecule, that is, it contains both a discrete polar portion and a well-defined non-polar fragment. A common surfactant used in shampoos is sodium lauryl sulfate. S O O O Na sodium lauryl sulfate simplified representation When a surfactant is added to water, the molecules orientate themselves on the water’s surface as shown in the diagram below. When even more surfactants are added, the surfactant molecules will group together in th ree-dimensional spherical clusters, with the hydrocarbon chains filling the interior of the cluster and the ionic ends composing the outer surface. These molecular conglomerations are known as micelles. (i) By identifying all favorable interactions, explain the molecular orientation of the surfactant molecules at the surface of the water. (ii) Explain how micelles help to remove grease from hair. [3]

3 © Hwa Chong Institution 2011 9647 / 03 / JC2 Prelim 2011 (b) Many shampoos, particularly those targeted fo r babies and children, claim to cause no eye irritation or sting. Compound A has been shown to be slightly effective as a “no- tears” formulation. The reaction scheme below outlines the synthesis of compound A. C11H23CO2H C11H23COCl H2NCH2CH2OH C11H23CONHCH2CH2OH SO3 C11H23CONHCH2CH2O S O O OH C11H23CONHCH2CH2O S O O O- + N OH HO HON OH HO HO Z II I III IV H N O H N O H H O lauramidopropyl betaine (i) State the reagent and condition needed for step I. (ii) State the type o