LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
B.Sc. DEGREE EXAMINATION – CHEMISTRY
SECOND SEMESTER – April 2009
CH 2504 / 2502 – HYDROCARBONS AND STEREOCHEMISTRY
Date & Time: 23/04/2009 / 1:00 – 4:00 Dept. No. Max. : 100 Marks
PART – A
Answer ALL the questions: (10 x 2 = 20)
- Write the structural formula for the following compounds.
- 3,3-Dimethyl-1-butene; b) But-2-en-1-ol.
- Classify the following into +M and –M group
2 , 2 , ,
- What happends when ethylchloride reacts with sodium metal.
- What is aromaticity Explain with an example?
- Specify the E and Z notation to the following compounds.
- a) b)
- What alkyl halide would yield each of the following pure alkene up on dehydro halogenation by a strong base. a) Isobutylene b) 3-methyl-l-butene.
- In Fridel-craft’s alkylation of benzene using n-propyl chloride gave only Isopropyl benzene rather than n-propyl benzene. Explain.
- Indicate which ring you would expect undergo nitration in phenylbenzoate.
- Write the structure of (i) Cis-4-tert-butylmethyl cyclohexane. (ii) cis-1, 2-dimethyl cyclohexane
- What are polynuclear aromatic compounds? Give two examples.
PART – B
Answer any EIGHT questions: (8 x 5 = 40)
- Write various possible structural formula of alkanes with molecular formula, C5H12 and write their IUPAC names.
- Discuss the different factors affecting the stabilities of carbocation (1o, 2o and 3o)
- Explain Bayer’s strain theory.
- How will you prepare cyclopentane using Dieckmann’s Synthesis.
- What are different conformation of cyclohexane. Draw their structure and explain the stabilities.
- How is ethylene prepared in the laboratroy? How does it react with
- i) Bromine water ii) Conc. H2SO4 iii) HCl (2+3)
- Explain the mechanism of Nitration of benzene.
- What is tautomerism. Explain mitro-acinitro tautomerism exhibited by Nitroethane.
- Explain by resonance structure that NO2 is meta directing, where as –OH group is Ortho-para directing towards electrophillic aromatic substitution.
- Explain the mechanism of Markownikoff’s Propene.
- i) How will you differentiate 1-butyne from 2-butyne.
- ii) Explain the mechanism of Hydroboration of propene.
- Write the structure of the product for the following reaction.
PART – C
Answer any FOUR questions: (4 x 10 = 40)
- a) Explain the type of hybridisation in the following
- i) Benzene ii) 1, 3 – buta-diene iii) cyclohexane iv) l-butyne.
- Which is more basic ethylamine or Aniline Explain.
- a) Explain Hyper conjugation.
- Arrange the compound in the increasing order of acid strength and Explain.
- CCl3 COOH ii) CH3 COOH, iii) CH3 CH2 CH2 COOH iv)CH2Cl OOH
- A hydrocarbon ‘A’ adds one mole of hydrogen in the presences of a platinum catalyst to form n-hexane. When A is oxidised vigourously with KMnO4, a single carboxylic acid containing three carbon atoms is isolated. Give the structure and name of A. Show your reasoning including equation for all reactions.
- i) Explain 1,2 – and 1,4 – addition of HBr with 1,3-butadiene.
- Write the mechanism Fridel – Craft’s Acylation
- i) Predict the product of Bromination of
- Acetanilide b) cinnamic acid
- Explain Diel’s Alder reaction taking suitable example.
- Draw various possible conformation of n-butane explain their stabilities based on energy level diagram?
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