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CHEMISTRY (HONOURS) Part-3
PAPER –VI
2011
1. (a) State and explain NMR spectroscopy and PMR signals.
(b) Explain shielding and deshielding of electrons.
(c) Explain chemicl shift.
(d) Explain PMR signal for 𝐶2 𝐻5 OH.
(c)Describe w ith an example, the use of organo-zinc
compounds to prepare a 𝛽-hydroxyester. Write the
mechanism.
(b)Explain the reactivity of methylene (𝐻2 C
diethylmalonate.
) group in
Using diethylmalonate, synthesise the following:
(i) Barbituric acid (ii) Glutonic acid
(a) Give two methods for synthesising a thioaicohol (R-SH)
and also two methods for a thioether (R-S<R).
(b) In between R-SH and R-OH, which one is more acidic and why?
(c) How would you convert R-SH to its corresponding sulfonamide?
5. (a)Write the mechanism for the preparation of osazone from glucose.
(b) How would you convert glucose to fructose?
(c)
Give two reactions of glucose in support of its ring
structure and two reactions in support of open chain structure.
6. (a)
Discuss Fisher indole synthesis.
(b) Explain, pyridine is stonger base than pyroole but weaker than aliphatic amines.
(c) Electrophilic substitution in pyrrole takes place at 2 position whereas it occurs
preferentially at 3-position in pyridine. Explain.
7. (a) What is a peptide linkage? what is geometry and bond length in a peptide molecule?
(b) Discuss the double helical structure of DNA.
8. Write short notes on the following:
(a) Soap and synthetic detergent
(b) Ziegler-Natta Polymerisation (c) Mutarotation
9. Distinguish
between
copolymerisation and
homopolymerisation giving examples Discuss various step
involved in the mechanism of –
(a) Free radical vinyl polymerisation ;
(b) Ionic vinyl polymerization.
10. (a) Write the electronic concept of colour and constitution
(b) How would you synthesise and three of the following :
(i) Methyle orange (ii) Malachite green
(iii) Crystal Violet (iv) Indigo
2009
1. (a) How is claisen condensation reaction employed to prepare a 𝛽-ketoester? Outline the
mechanism of the reaction. Show how you can synthesize ethylbenzoyl acetate and diethly
phenyle malonate using crossed Claisen condensation,
(b) (i) Show how 1,3-dithianes can
O
be used to synthesize ketones
||
or general formula
R — C—C𝐻2 —R1
(ii) Outline the conversion :
Benzldehyde —> acetophenone
2. (a) How can you employ Grignard synthesis in three different ways to get 3-phenyIe-3pentanol? Discuss the mechanism of the reaction that you employ.
(b)Describe with an example the use of orgnozinc compounds to prepare a 𝛽hydroxyester. Write the mechanism, of the reaction.
3. (a) Give one general method each for the preparation indole, quinoline and isoquinoline.
Discuss of mechanism of the reactions.
(b) Account for the observations:
(i) Pyridine is stronger base than pyrrole, but weaker than aliphatic amines
(ii) Electrophilic substitutionin pyrrole takes place the 2-position, whereas it occurs
preferentially the 3-position in pyridine.
4. (a) What products are obtained by the action phenylhydrazine on D-glucose, Dfructose and mannose? Discuss the mechanism of the reaction involved in the above
mentioned changes.
(b) How will you bring about(i) The interconversion of glucose and fructose;
(ii) Chain lengthening and chain shortening in aldose.
5. (a) What is a peptide linkage? What is the geometry bond lengths in a peptide molecule?
(b) What are the protecting agents employed in the peptide synthesis? Illustrate their roles
in the synthesis polypeptides.
6. Distinguish between copolymerizatio homopolymerization giving examples. Discuss
various step involved in the mechanism.of(a) free-radical vinyl polymerization;
(b) ionic vinyl polymerization.
7. Write notes on :
(a) Mutarotation
(b) Condensation polymerization
(c) Configuration of monosaccharides
8. (a) Explain the observations :
(i) 𝐶2 𝐻5 𝑆 0 is more powerful nucleophile than 𝐶2 𝐻5 𝑂0
(ii) 𝐶2 𝐻5 SH is stronger acide than 𝐶2 𝐻5 OH
(iii) RSH undergoes oxidative coupling while ROH does not
(b)Identify L, M, X, Y and Z in the following sequence:
(i) Benzyl bromide + thiourea —> L
(ii) L + OH/𝐻2 O and then H+ → 𝑀
(iii) M + 𝐻2 𝑂2 → 𝑋 (iv) X+NaOH→ 𝑌
(v) Y + benzyl bromide —> Z
9. (a) Discuss modern theories of colour and constitution
(b) How can you synthesize
(i) methyl orange, (ii) crystal,
violet, and (iii) phenolphthalein?
10. (a) Explain the term 'chemical shift'.
(b) How many PMR-signals would you expect from the following compounds?
(i) 1, 1-dimethyl cyclopropane ii) 1, 2-dibromopropane (iii) trans-2-butene
(iv) 1-pentene
(c) Sketch giving reasons the PMR-speetra of (𝐶𝐿2 𝐶𝐻)3,(𝐶𝐻3 )2 CHI,C𝐻3 ,CHC𝐿2 and
C1 C𝐻2 C𝐻2 C𝐻2 C1, showing he splitting patterns and relative positions of each signal.
2008
1. (a) Write the mechanism involved in the conversation of 𝐶𝐻3 𝐶𝑂𝑂𝐶2 𝐻5
to 𝐶𝐻3 . 𝐶𝑂. 𝐶𝐻2 . 𝐶𝑂𝑂𝐶2 𝐻5 .
(b) how to Diethyl malonate prepared from potassium cyano acetate?
(c) Write the tautomericstructuresfor the Folloing:
(i)
Nitrometehene (ii)oxime of acetaldehyde
(iii) Phenol
d) Using diethyl malonate, synthesise the folloing :methyl butanoic acid (ii) Glutaric acid, ((𝐶𝐻2 )3 (𝐶𝑂𝑂𝐻)2 (iii) Barbituric acid
2. a) Give evidences favoring the cyclic structure for glucose.
b) Determine the pyranox structure of glucose.
c) Give one method of converting an aldohexase to an aldopentose.
d. Give examples of stereoisomers which are :
i) Epimers
ii) Anomers
3. Write comprehensive notes on any three of the following :
a) Mutarotation
b) Furan
c)Disaccharides
d) Keto-enoltautomerism
4. (a) Briefly discuss the modern concept regarding colour constitution.
(b)How will you synthesise the following?
i) Congored from benzidine
ii)indigo from anthranilic acid
(c) Why does phenolphthalein in show pink color to n alkaline solution?
5. (a) Synthesise :
(i)
𝐶𝐻3 − 𝐶𝐻 − 𝐶𝐻2 − 𝐶𝑂𝑂𝐶2 𝐻5 from 𝐼 − 𝐶𝐻2 − 𝐶𝑂𝑂𝐸𝑡
|
OH
O
||
(ii)
(iii)
𝑅1 − 𝐶 − 𝑅2 from 𝑅1 COOH and 𝑅2 𝐿𝑖
𝑅2 𝐶𝑂 from RLi and 𝐶𝑂2
(b) How does ethyl magnesium iodide react
O
𝐶𝐻3 − 𝐶𝐻 − 𝐶𝐻2 ?
With
(c) Compleatethe following reactions : 3 + 2 = 5
O
||
(i)
𝐶𝐻3 − 𝐶 − 𝐶𝐻2 − 𝐶𝐻2 − 𝐶𝐻2 𝑂𝐻 + 𝐶𝐻3 𝑀𝑔𝐵𝑟 − ?
(1 mol)
(1 mol)
Br
𝐶𝐻3 𝑙 ∶
(i)
Cl
CH
𝑀𝑔 𝑎𝑛𝑑 𝑒𝑡ℎ𝑒𝑟
6. (a) how will you synthesise 2, 4, 6- tri-methyl pyridine starting from EAA,
ammonia and acetaldehyde ?
(b) Which one is the stronger abse and why ?
(i) Pyridine
(ii)Quinoline
(c) At which points pyridine is attacked by an electrophile and why?
(d) Discuss Skraup synthesis for quinolone.
7. (a) Give IUPAC name for the compound.
𝐶𝐻3
CH - 𝐶𝐻2 – SH.
𝐶𝐻3 of R–Shand R-OH.
(b) Compare the acidic nature
(c) Write and equation showing desulphurization of R- S- R.
(d)Suggest method to convert RSH to its Corresponding also sulphonamide.
(e)Give two methods for synthesisinga thioalcH and also two methods for a
thiorther R- S- R.
(f) How can ethane thiol beconverted to a mercaptal and a mercaptol.
8. (a) Discuss the mechanism of the following polymerization reactions:
Peroxide
(i)
Vinyl benzene or styrene ————— ?
H+
(ii)
2-methyl propene ——— ?
(b)Describe, in brief, the role of Ziegier-Natta catalyst' polymerisation reactions.
9. (a) How is ana -amino acid is synthesised by Gabriel's Phthalimidereaction ?
(b) Explain the terms isoelectric point for an amino acid R-CH.'NH-COOH.
(c) Explain, with example, denaturation of proteins.
(d) Give an-account of nucleic acids.
10. (a) Explain the terms diamagnetic anisotropy.
(b) What is meant by 'splitting of a signal' in NMR spectroscopy? How many
splittings in the signals are expected for the protons
in 1. l-dichloroethane and I-brome - 2, 2 - dimethylpropane ?
(c) Discuss, in brief, the term coupling constant.
(d) Calculate the rations of the different kinds of protons in a compound with an
intergral ratio of 4 : 18.4: 16 (going from left to right across the spectrum)