Edexcel Jan 2014 (IAL) Paper 5 Q23 (with explained solutions) |

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Edexcel Jan 2014 (IAL) Paper 5 Q23

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23 Compound P is a white crystalline solid with the following percentage composition by mass. Element carbon hydrogen oxygen nitrogen % composition by mass 40.44 7.87 35.96 15.73 (a) Calculate the empirical formula of P. You must show your working. (3) 16 *P42993A01628*<br />
(b) The mass spectrum of P is shown below. Relativity intensity 100 80 60 40 20 0.0 0.0 20 40 60 80 100 (i) Label the molecular ion on the mass spectrum using the symbol M+. (ii) Deduce the molecular formula of P. m/e (1) (1) *P42993A01728* 17 Turn over<br />
(c) P was dissolved in sodium carbonate solution and, on heating, a colourless gas, which turned lime water cloudy, was very slowly evolved. When an aqueous solution of P was mixed with an aqueous solution of copper(II) sulfate, the blue colour of the copper(II) sulfate solution darkened. (i) Use the results of these two experiments to deduce the functional groups that are present in P. Explain your answers. (4)(ii) There are several compounds which have the formula you have deduced in (b)(ii) and contain the two functional groups you have identified in (c)(i). Draw the structural or displayed formulae of two of these compounds. (2) 18 *P42993A01828*<br />
(iii) The nuclear magnetic resonance spectrum of compound P is shown below. (cid:303)/ppm This part of the spectrum only shows the peaks due to the hydrogen atoms which are attached directly to carbon atoms. Use this spectrum to deduce the structure of P. Justify your answer. (2)(d) Explain why P is a solid at room temperature and pressure. (1)(Total for Question 23 = 14 marks) TOTAL FOR SECTION B = 50 MARKS *P42993A01928* 19 Turn over<br />

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Acceptable Answers Reject Mark Question Number 23(a) Elem ent C mol Ratio 40.44 12 = 3.37 7.871 = 7.87 35.9616 = 2.2475 2.00 15.7314 = 1.12357 (1) (1) Empirical formula = C3H7O2N (1) Symbols in any order Stand alone mark No TE on incorrect ratio IGNORE significant figure and rounding errors except 1sf in mole calculation 2.99 9 7.00 4 0 1.00 0 Reject Mark Question Number 23(b)(i) Peak at m/e = 89 labelled M+ Acceptable Answers ALLOW Any clear label e.g. C3H7O2N+ Question Number 23(b)(ii) Mr = 89 = Mr (C3H7O2N) so molecular Acceptable Answers formula is C3H7O2N Symbols in any order IGNORE structural and displayed formulae Reject Mark Answer with no explanation Mr = 90 C3H7O2N+<br />
Acceptable Answers Question Number 23(c)(i) Gas evolved is carbon dioxide / CO2 (1) (so carboxylic) acid / -COOH group is present (1) Dark blue colour indicates the formation of a (copper(II)) complex ALLOW indicates ligand exchange has occurred (1) Suggests that an amine / -NH2 group is present ALLOW NH (1) IGNORE ammine amino acid Reject Mark NH3 complexes Amide group<br />
Acceptable Answers Question Number 23(c)(ii) Any 2 of A, B, C or D (1 mark for each) Molecules Zwitterions Or fully displayed structures Reject Mark<br />
Question Number 23(c)(iii) Acceptable Answers First mark P has structure A or Second mark EITHER Splitting pattern quartet due to CH next to CH3 and doublet due to CH3 next to CH ALLOW A comparison e.g A has quartet & doublet but B has two triplets OR As the areas / heights of the two peaks are in a 3:1 ratio (approximately), there must be 3 protons in one environment and 1 in another No TE if A is not one of the isomers given in (c)(ii) Acceptable Answers P (is an amino acid) exists as a zwitterion ALLOW Zwitterion formula OR molecules are held together by (strong) ionic forces IGNORE Just electrostatic forces Question Number 23(d) Reject Mark Just quartet & doublet Just two peaks Reject Mark Total for Question 23 = 14 marks Total for Section B = 50 mark<br />
Section C Question Number Question Number Acceptable Answers / CH3Cl / CH3Br / CH3I Acceptable Answers 24(a)(i) M = chloro- /bromo- / iodo- methane 24(a)(ii) CH3X + AlCl3CH3Ignore curly arrows even if incorrect Ignore state symbols even if incorrect + + AlXCl3 Reject Reject Mark Mark<br />
Ques. No. 24(a) (iii) Acceptable Answers Reject Mark Curly arrow on or outside the hexagon Dotted bonds to H and CH3 + including to the + TE on incorrect electrophile in (a)(ii) If benzene used instead of methylbenzene OR If final product not 1,2-dimethylbenzene (max 2) Curly arrow from on or within the circle to positively charged carbon ALLOW Curly arrow from anywhere within the hexagon Arrow to any part of the CH3 charge (1) Intermediate structure including charge with horseshoe covering at least 3 carbon atoms, and facing the tetrahedral carbon and some part of the positive charge must be within the horseshoe (1) Curly arrow from CH bond to anywhere in the benzene ring reforming delocalized structure (1) Correct Kekul structures score full marks Ignore any involvement of AlX4in the final step<br />

Question 21 22 23 24

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