1 a) Name the following substances with the used common names or according to IUPAC (4p): b) Draw detailed structures of the substances below.

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1 EGLIS VERSI Exam rganic Chemistry 2 (KD1100) Wednesday May 21, 2008, Allowed answering aid: molecular models Periodic system and tables of bond energies, pk a -values and MR-shifts are attached after the questions Total of 10 questions, each worth 10p (total 100p). Requirements: A p B 80-89p C 70-79p D 60-69p E 50-59p Fx 45-49p F 0-44p A supplementary exam will be arranged for students with results of 45-49p. This exam will take place on Wednesday June 4, 2007, at in the Erdtman-room, rganic Chemistry, Teknikringen 30, Level 7. o special registration necessary. Please note that the minimum requirement for the course have to be demonstrated in this case also. The make-up exam will take place on Thursday August 28, Answer every question on separate sheets to facilitate grading write name, programme and year on each sheet Motivate your answers, normally both text and figures are necessary Please observe that the questions are not necessarily organized in order of difficulty (question 10 is not essentially the most difficult!) Good luck! lof Ramström 1 a) ame the following substances with the used common names or according to IUPAC (4p): MgBr b) Draw detailed structures of the substances below. (4p) o lithium aluminum hydride o an aromatic cation with 6 π-electrons o the most stable enol of pentane-2,3-dione o the hydrate of benzaldehyde c) ow is ückel s rule formulated and what is meant by the n (2p) 1 (9)

2 EGLIS VERSI 2 a) Draw the π-orbital levels for the enolate ion. Indicate the approximate form of each orbital, how many electrons they contain, and what orbital constitute the M. (7p) b) Which of the orbitals of the enolate ion reacts with the electrophile in a typical aldol addition (1p) c) Explain briefly why the enolate ion preferentially reacts from the C-atom and not from the -atom. (2p) 3 Complete the following reaction sequence. o mechanisms required. (2p per correct structure) Br + A C Br Mg ether B C 6 11 Mg 2 Br 1) 2) +, 2 E C 3 C D C C C Acetylcholine acts as a transmitter substance at the transfer of nervous impulses (neurotransmitter) between nerve cells. After the transfer, the substance is quickly degraded to inactive components, a reaction that can take place at neutral p. Acetylcholine may otherwise be degraded in as well acidic as basic solution. Describe with detailed mechanisms how the hydrolysis of acetylcholine occurs in acid and base, respectively (3p each), and design a possible mechanism for how the enzyme acetylcholinesterase can catalyze the hydrolysis at neutral p (4p). a) +, 2 b) -, 2 c) acetylcholinesterase, 2 2 (9)

3 EGLIS VERSI 5 Imines are nitrogen analogs of carbonyl compounds and behave similarly in many reactions. a) Describe with mechanism how the imine below can be prepared from a suitable carbonyl compound. (4p) F 3 C b) ow does the following reaction proceed Indicate reagents and mechanism. (4p) + c) Propose reagents for the synthesis of Meclizine outlined below. Meclizine is an antiemetic that can be used for motion sickness. (2p) Meclizine 6 a) Sketch out the 1 -MR spectrum for the substance below (diisobutylcarbonate). (4p) b) Analysis of the compound X resulted in the following data: Molecular formula = C Index of hydrogen deficiency (ID) = 5 (= number of double bond equivalents, DBE) The IR spectrum indicated no absorption in the area cm -1 (no -groups) and strong absorption at 1720 cm -1 (C= group). 3 (9)

4 EGLIS VERSI The 1 -MR spectrum showed five signals: 7,2-7,3 ppm, 5, multiplet 3,9 ppm, 1, quartet 3,7 ppm, 2, singlet 3,3 ppm, 3, singlet 1,3 ppm, 3, doublet What structure has the substance X Draw the 1 -MR spectrum and indicate what proton signal corresponds to what proton. (6p) 7 a) Polystyrene can be produced from styrene using free radical polymerization, describe briefly the mechanism. AIB is a radical initiator that in presence of light or heat generates radicals. You may use A. to describe these. The parenthesis and the letter n means that the structure is repeated n times. (4p) styrene AIB light or heat n polystyrene b) Describe with mechanism what happens in the reaction below. What is this reaction type (6p) n + Al 3 8 A benzophenone structure was used as starting material in the synthesis of Meclizine mentioned above. Design a synthetic route to this substance starting from benzene and suitable reagents. The synthesis may proceed in many steps, but indicate possible weaknesses and byproducts in each step. (10p) 4 (9)

5 EGLIS VERSI 9 a) itromethane (C 3 2 ) has a relatively low pk a -value. Draw the reaction between nitromethane and suitable base (B) and explain briefly why the pk a is low. (2p) b) itromethane can be used as a reagent to produce noradrenaline (norepinephrine), a transmitter substance in the sympathetic nervous system. Complete the synthetic sequence below and indicate the reagents/reactants 1, 2, 3 and the byproduct 4. Describe the mechanism in the last step in detail. o consideration of stereochemistry required. (6p) 3 C 2 nitr omethane noradrenaline + 4 c) What can be formed if the intermediate product after the first step is treated with the reagents in the last step o mechanisms required. (2p) The Biginelli reaction is a so called multicomponent reaction named after the Italian chemist Pietro Biginelli who developed it already in 1891 (Chem. Ber. 1891, 24, 1317). The reaction gives rise to dihydropyrimidones, which often are of pharmaceutical value. Propose with detailed mechanisms and suitable reagents how the Biginelli reaction to the dihydropyrimidone BP below occurs. Use the three starting materials S1, S2 and S3. (10p) BP 2 2 S1 S2 S3 5 (9)

6 6 (9) EGLIS VERSI

7 EGLIS VERSI Average Bond Strengths Bond Dissociation Energies (BDE) Average Bond Dissociation Energies (kcal/mol) C F Si S Br I a C b 73 c 86 d 116 e 72 f c h a 86 d 53 h F e Si f S Br I a b c d e f Average value. Approximately 103 kcal/mol for alchols and 119 kcal/mol for water C=C 146 kcal/mol C C 200 kcal/mol C= 147 kcal/mol C 213 kcal/mol C= 176 kcal/mol for aldehydes and 179 kcal/mol for ketones C=Si 111 kcal/mol = 111 kcal/mol 226 kcal/mol Release of strain energy upon ring opening Cyclopropane 27 kcal/mol Cyclobutane 26 kcal/mol Epoxide 25 kcal/mol Aromatization energy Benzene 36 kcal/mol Pyridine 28 kcal/mol Delocalization of lone pair Carboxylic ester ~7 kcal/mol Carboxylic amide 17 kcal/mol ydrogen bonds 4-10 kcal/mol (usually) 7 (9)

8 EGLIS VERSI SME APPRXIMATE pk a VALUES C -10 Strong Mineral Acids <0 F 3 C 12 (C) 3 C C CF 3 C 2 R C R S 2 3 C R R R C R C R C C 25 RS 11 R 2 ~30 9 (C 6 5 ) 3 PC 3 35 RS R (I-Pr) 2 R C > R R 13 8 (9)

9 EGLIS VERSI CARACTERISTIC PRT CEMICAL SIFTS* Type of Proton Structure Chemical Shift, ppm Tetramethylsilane (TMS) (C 3 ) 4 Si 0 Cyclopropane C Primary R-C Secondary R 2 -C Tertiary R 3 -C 1-2 Amino R ydroxylic R-C- 1-6 Allylic C=C-C Esters -C-CR Acids -C-C 2-3 Carbonyl Compounds -C-C= 2-3 Acetylenic C C- 2-3 Benzylic Ar-C- 2-3 Iodides -C-I 2-4 Bromides -C-Br Alcohols -C- 3-4 Ethers -C-R 3-4 Chlorides -C- 3-4 Esters RC-C Vinylic C=C- 4-6 Fluorides -C-F Phenolic Ar Aromatic Ar- 6-9 Aldehydic R-(-)C= 9-10 Enolic C=C Carboxylic RC * Fritt modiferad från: 9 (9)