COVENANT UNIVERSI TY ALPHA SEMESTER TUTORIAL KIT (VOL. 2) P ROG RAMME: CH EMI ST RY 300 LEVEL 12 DISCLAIMER The contents of this document are intended for practice and learning purposes at the undergraduate level. The materials are from different sources including the internet and the contributors do not in any way claim authorship or ownership of them. The materials are also not to be used for any commercial purpose. 12 LIST OF COURSES CHM312: Organic Chemistry CHM315: Unit Operations/Heat Transfer CHM317: Environmental Chemistry CHM332: Industrial Inorganic Chemistry CHM333: Instrumental Method of Analysis CHM334: Applied Spectroscopy CHM356: Metallurgy and Metal Fabrication *Not included 12 COVENANT UNIVERSITY CANAANLAND, KM 10, IDIROKO ROAD P.M.B 1023, OTA, OGUN STATE, NIGERIA. TITLE OF EXAMINATION: BSc EXAMINATION COLLEGE: Science and Technology DEPARTMENT: Chemistry SESSION: 2015/2016 SEMESTER: ALPHA COURSE CODE: CHM 312 CREDIT UNIT: 3 COURSE TITLE: Organic Chemistry INSTRUCTION: Attempt any FOUR (4) Questions TIME: 3 HOURS PLEASE START THE RESPONSE TO EACH QUESTION ON A NEW PAGE OF THE ANSWER BOOKLET 1. (a) Describe the Haworth synthesis of Naphthalene. (5 marks) 12 Haworth Synthesis • Naphthalene can be synthesized by treating benzene with succinic anhydride in the presence in the presence of AlCl . 3 O O C COOH O AlCl3 Zn/Hg COOH HCl 3-Phenyllpropa- Benzene O 3-Benzoylpropa- noic acid Succinic noic acid anhydride Conc. H2SO4 Pd/C or Zn/Hg Selenium HCl O dehydrogenation Naphthalene 1,2,3,4-Tetrahydro naphthalene (b) Showing the appropriate equation, give the final products of sulfonation of anthracene both at low and high temperature. (5 marks) Sulphonation SO3H SO3H exceLsosw CToenmcp. eHr2aStuOre4 Anthracene-1,8-disulphonic acid eHxcigehs sT eCmonpce.r aHt2uSreO4 HO3S SO3H Anthracene-2,7-disulphonic acid (c) Give the IUPAC names of the following compounds: 12 (i) Br O (ii) CH (iii) O O (iv) O 3 CH C CH O CH C C C 3 H C CH Br H C CH C H C O CH H C NH 3 2 3 2 3 3 3 2 O (2 marks) (i) 3-bromobutanoyl bromide; (ii) isobutyl acetate or 2-methylpropyl ethanoate or - bromobutyryl bromide; (iii) acetic anhydride; (iv) acetamide (d) Give the general products formed during the hydrolysis, alcoholysis, and aminolysis of acid halides. (3 marks) Hydrolysis, alcoholysis and aminolysis of acid chloride will give the products: carboxylic acid, ester and amide respectively as shown in the figure below; Acid Chloride Reactions (1) O HO 2 R C OH + HCl acid O R'OH O R C OR' + HCl ester R C Cl O R'NH 2 R C NHR' + HCl amide O O R'COOH R C O C R' + HCl acid anhydride => Chapter 21 16 (e) Complete the following reactions: (i) CH CH COOH + NaOH ? 3 2 CH3―CH2―COOH + NaOH CH3―CH2―COO Na+ + H2O sodium propanoate 12 O C (ii) OCH3 HCl + H O 2 (2.5 marks) [Total 17.5 marks] 2. (a) Write structures for the following bicyclic alkanes: (3 marks) (i) bicyclo[1.1.0]butane; (ii) 2-chlorobicyclo[3.2.0]heptane; (iii) 7- methylbicyclo[2.2.1]heptane H C Cl 3 (b) (i) Draw the Newman projections for rotation about the C―C bond in chloroethane and clearly label the most stable conformer and the least stable conformer (2 marks) Cl CCllH H H H H H HH HH H H more stable The barrier to rotation about the C―C bond in chloroethane is 18.0 kJ/mol. 12 (ii) What energy value can you assign to an H―Cl eclipsing interaction given that H―H eclipsing interaction is 4 kJ/mol? (2 marks) 18 = 𝑥 +4+4 = 𝑥+8 𝑥 = 18−8 = 10 kJ/mol (iii) Sketch a diagram of potential energy versus angle of rotation about the C―C bond of chloroethane. (2 marks) 18 kJ/mol E 0 60 120 180 240 300 360 Degrees of Rotation  (iv) Label the energy barrier to rotation on your diagram (1 mark) See diagram above (c) (i) The relative basicities of some nitrogen-containing compounds are as follows: CHNH > NH > CHNH. Explain why these compounds behave as 2 5 2 3 6 5 2 bases. (2 marks) There is a lone pair of electrons on nitrogen that can be donated to a proton (ii) Using diagrams, explain why aniline (CHNH) is more acidic than ammonia 6 5 2 (NH). 3 (2 marks) The lone pair of electrons on nitrogen is delocalized into the benzene ring, which means that the lone pair of electrons is not available for donation to a proton. 12 + NH2 NH2 (d) This question is about Diels-Alder reaction, a [4+2] cycloaddition reaction involving a diene and a dienophile. Use curly arrows to describe the mechanism of the reaction between 1,3-butadiene and propanal to give cyclohex-3-ene carbaldehyde. (3.5 marks) CH 2 CH 2 H H CH 2 O O [Total 17.5 marks] 3. (a) An aldol addition product loses water to form an aldol condensation product. Give the mechanism of reaction for aldol condensation of propanal (CHCHCHO). 3 2 (10 marks) Aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone. (b) Briefly define the following terms showing the equation of reactions (i). Claisen condensation (ii). Malonic ester synthesis 12 (iii). Aldol condensation (iv). Aldol addition reaction (v). Enol (7.5 marks) [Total 17.5 marks] The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone. Aldol condensation is an organic reaction in which an enol or an enolate ion reacts with a carbonyl compound to form a β-hydroxyaldehyde or β-hydroxyketone, followed by a dehydration to give a conjugated enone. Aldol addition In the aldol reaction, two molecules of an aldehyde or ketone react with each other in the presence of a base to form a -hydroxy carbonyl compound. Malonic Ester Synthesis Four basic step in reaction 1. Enolate formation (strong base) 2. Enolate alkylation (alkyl halide) 3. Ester hydrolysis (aqueous acid) 4. Decarboxylation (heat) Enols are isomers of aldehydes or ketones in which one alpha hydrogen has been removed and placed on the oxygen atom of the carbonyl group. The molecule has a C═C and an ―OH 12