SRJC H2 Chem 2012 Prelim P3 QP

1 SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2 CANDIDATE NAME CLASS CHEMISTRY 9647/03 Preliminary Examination 22 August 2012 Paper 3 Free Response Questions 2 hours Additional Materials: Data Booklet Writing Papers READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough work. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. 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 the brackets [ ] at the end of each question or part question. At the end of the examination, fasten all your work securely together with the cover page provided. This document consists of 13 printed pages and 1 blank page 2012 JC2 PRELIM 9647 P3 Turn Over]

2 2012 JC2 PRELIM 9647 P3 Turn Over] Answer any four questions 1 (a) Aqueous sodium hydroxide is an important reagent in many organic reactions where the hydroxide ion can act as both a base and a nucleophile. In the Reimer-Tiemann reaction, phenol is heated with chloroform in the presence of aqueous sodium hydroxide to give 2-hydroxybenzaldehyde, compound B . The reaction involves the formation of a reactive intermediate, CCl2, through an acid- base reaction. CHCl3 + OH- ® CCl2 + H2O + Cl – chloroform (i) State the type of reaction that occurred in reaction I. (ii) Suggest a chemical test to differentiate compound s B and A under room conditions. (iii) Compound B can undergo further reaction to form the product below. Name and describe the mechanism involved, using curly arrows to show the movement of electrons and indicating all charges. (iv) Comment on the relative acidity of phenol and compound B. [9] NaOH (aq) heat II OH + CCl2 OH CHCl2 OH CHO B A I OH C OH CN H B OH CHO

3 2012 JC2 PRELIM 9647 P3 Turn Over] (b) Besides its exten sive use in organic chemistry, aqueous sodium hydroxide is also used in photographic development. The black-and-white photography process involves four steps: Step 1 Photo-taking: Interaction of light with silver halides (AgX) on film. Step 2 Developing: Redox reactions to develop the actual image. Step 3 Fixing: Changing the solubility of chemical compounds with different conditions to preserve the image on the film. Step 4 Printing: Shining light through the film onto phot