OCR A Jan 2013 Paper 4 Q4

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4 Acid anhydrides are organic compounds that can be reacted with alcohols to form esters and carboxylic acids. 15 Compound F, shown below, is an acid anhydride used in the perfume industry as a starting material in the production of esters. compound F Compound F is a mixed acid anhydride, formed from two different carboxylic acids. (a) A chemist reacts compound F with an alcohol, G. HO alcohol G (i) Name alcohol G.[1] (ii) The reaction between F and G forms a mixture of four organic compounds. Two of the compounds are esters, and two are carboxylic acids. One of the esters is shown below. Draw the structures of the other three organic compounds formed.OCR 2013 [3] Turn over<br />
 (b) After the reaction in part (a), the chemist wished to analyse the mixture by separating the compounds using gas chromatography (GC), and measuring their retention times. 16 (i) State what is meant by retention time.[1] (ii) What are the possible limitations of this analysis by GC?[1] (c) Polyanhydrides are condensation polymers that have been recently developed for use in the pharmaceutical industry. The polyanhydride, PAPA, is used to form a protective coating around some anti-cancer drugs. A section of the polymer chain of PAPA is shown below. (CH2)7 (CH2)7 (CH2)7 (i) In the diagram above, draw a box around a repeat unit of PAPA. [1]OCR 2013<br />
 17 (ii) The PAPA coating is degradable and breaks down to form the dicarboxylic acid HOOC(CH2)7COOH. Name the type of reaction that occurs when PAPA degrades.[1] (iii) PAPA-coated tablets can be stored for a long time in blister packets. Scientists can detect whether PAPA has degraded using infrared (IR) spectroscopy. Outline how IR spectroscopy could be used to determine if PAPA has degraded. Include in your answer the wavenumber range of any characteristic absorptions that would be seen.[2] (iv) The dicarboxylic acid, HOOC(CH2)7COOH, can react with benzene-1,3-diol to form a condensation polymer. Draw one repeat unit of this condensation polymer. END OF QUESTION PAPEROCR 2013 [3] [Total: 13]<br />

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