LOYOLA COLLEGE (AUTONOMOUS), CHENNAI – 600 034
DEGREE EXAMINATION –CHEMISTRY
SECOND SEMESTER – APRIL 2007
CH 2502 – HYDROCARBONS AND STEREOCHEMISTRY
Date & Time: 20/04/2007 / 1:00 – 4:00 Dept. No. Max. : 100 Marks
PART – A
Answer ALL the questions (10 x 2 = 20)
- Classify the following into +I and –I group: isopropyl, cyano, methoxy and
- Write the structural formula for the following compounds
- a) 1-hydroxy-2-propanone b) 3,5-octadiene
- Arrange the following acids in the increasing order of the acid strength and justify your answer: (CH3)3C-COOH, H-COOH and CH3-COOH.
- Mention the differences between inductive effect and inductomeric effect.
- Why is fluorination faster than chorination of alkane?
- What is aromaticity? Explain with an example.
- Why does maleic acid give anhydride readily and fumaric acid gives its anhydride only on heating?
- Specify the E and Z notation to the following compounds:
- What are the two alkyl halides formed on the addition of HCl to 3-methyl-1-butene?
- What are polynuclear aromatic compounds? Give two examples.
PART – B
Answer any Eight questions (4 x 5 = 20)
- Write various possible structural formulae of alkanes with molecular formula, C6H14 and write their IUPAC names.
- Discuss the different factors affecting the stability of free radicals (primary, secondary and tertiary).
- Explain Baeyer’s strain theory and theory of strainless ring.
- Write short notes on i)Wurtz synthesis of hydrocarbons ii) Dieckmann’s synthesis of cycloalkanes.
- What are the different conformers of cyclohexane? Give the structures and discuss which structure is more stable.
- How is ethylene prepared in the laboratory? How does it react with i)bromine water ii) Con.H2SO4 iii) HCl iv) acidified KMnO4 v) hypochlorous acid vi) ozone
- Explain the mechanism of electrophilic substitution of (i) Friedal-Crafts acylation (ii) sulphonation of benzene.
- What is tautomerism? Explain keto-enol tautomerism in detail.
- Why carboxyl group is meta orienting and carboxylate ion is ortho and para directing?
- How will you prepare the following:
- n-propanol from propene (ii) Glycol from ethylene.
- Explain the mechanism of markownikoff and antimarkownikoff addition of propene.
- Write the structure of the product in the reaction of
2-pentyne Alkaline. KMnO4
PART – C
Answer any FOUR questions (4 x 10 = 40)
- Explain the mode of hybridization of carbon in methane, ethylene and acetylene. Explain why aliphatic amines are more basic than aromatic amines.
- Explain the mechanism of halogenation of alkanes and what are the factors affecting the rate of the reaction.
- a) Why does the electrophilic substitution reaction of naphthalene take place in the carbon1(α) rather than on carbon 2 (β)
- b) Explain the 1,4- and 1,2- addition reactions of dien in detail.
- On reduction of compound C6H10(A) gives first C6H12(B) and finally C6H14(C). On ozonolysis followed by reduction (A) gives two aldehydes C2H4O (D) and C2H2O2 (E). Oxidation of B with acidified potassium permanganate gives the acid C3H6O2(F), Identify the compounds A to F and express the various reactions involved by means of equations.
- a) What is orientation effect? Explain with examples.
- b) Write short notes on i)Diels – Alder reaction ii) Hydroboration reaction.
- Write the Newman projection formulae of comparatively stable conformation of butane. Which one of them is preferred conformation?
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