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INDIAN INSTITUTEOF TECHNOLOGYKHARAGPUR

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EXAMINATION ( Mid Semester / End Semester) 1 SEMESTER( Autumn / Spring)

Roll Number I Section I I Name

C Y 1 1 0 0 1 Subject NameSubject Number CHEMISTRY

Name of the Department/Centre of the student

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To be filled in by the Examiner

Question Number 1 2 3 4 5 6 7 8 9 10 Total

Marks obtained

Marks obtained (in words) Signature of Examiner Signature of Scrutineer

1

1. (a) The threshold wavelength for the ejection of photoelectrons from sodium metal is 5420 A. Calculate thevelocity of photoelectrons ejected by light of wavelength 4000 A. [3 Marks]

(b) Write the Hamiltonian for H2+molecule. [2 Marks]

(c) The de Broglie wavelength of an electron is 10-8 cm. Calculate its kinetic energy in eV.

[Useful values: me = 9.1 x 10-28g; h = 6.626 x 10-27 erg sec; 1 erg = 6.242 x 1011eV] [2Marks]

(d) Carbon monoxide (CO) molecule binds to metal ion through carbon atom. Justify the statement fromthe molecular orbital diagram of CO. [4 Marks]

(e) Find the normalization constant for the bonding MO of Hz molecule. [2 Marks]

2

2. (a) ~H(hydration)of Fe+2 ion is 50 kllmol higher than would be expected if there is no CFSE. Find themagnitude of ~o for high spin complex [Fe(OH2)6]2+. [3 Marks]

(b) Draw the distorted d-orbital splitting diagram for high spin ct ([ML6] type) complex ion. Whichdistortions between z-in and z-out are energetically favourable? [4 Marks]

(c) The electronic spectrum of [Ti(OH2)6]3+ shows two bands in UV-visible region. Explain. [2 Marks]

(d) Assume [Cd(NH3)4]2+ is formed by stepwise reactions and it has KI = 10265,K2 = 10210,K3 = 10144andK4 = 10125 at 25°C. The overall enthalpy change (~HO) for formation of [Cd(NH3)4]2+ is -53.2 klrnol'. Calculatethe change in entropy (~SO) at 25°C. (Given R = 8.314 Jmol-1X-I). [4 Marks]

(e) Write down the structure of a metal complex used in chelation therapy. [2 Marks]

5

3. The Latimer diagram for manganese in acidic solution is given below at 25°C. Draw the Frost diagram andcomment on the stability of Mn3+ in acidic medium. [10 Marks]

? 2.26 V 0.95 V ? -1.18 V

Mno4----Mno42-~---Mn02 (s)---Mn3+---Mn2+---Mn (s)

1.69 V 1.23 V

8

4. What is the common name of the following reactions?

(a)+

(b)

CIPh3P",-, I ..'",CI

PdPh/ I "PPh3

CI

Ph3P", ""CIPd' +

CI/ "PPh3

PhCI

[3 Marks]

(b) What are the valence electrons of the metals in the following complexes? Use the 18 electron rule: (i)Fe2(CO)9 (ii) RU2(CO)12 (iii) Na[HFe(CO)4]. [3 Marks]

(c) (i) Show the reaction scheme for the addition of dihydrogen to [(lrCl(CO)(PPh3)2] with chemical structures.

(ii) What are the oxidation states of the metal (both for reactant and product)? [2 + 1 = 3 Marks]

(d)

(e)

How Wilkinson's catalyst is synthesized in laboratory? Write the reaction.

Wilkinson's catalyst is an organometallic compound. Justify the statement.

[2 Marks]

[I Mark]

11

5. (a) Assign the absolute configuration (RIS notation) for the following molecules showing the prioritysequence at their respective chirality carbon(s) [6 Marks]

i)HO H~

.•2" ii)

OH

"/yOXCI

H CI(b) Indicate the relationship between i) A & B; ii) C & D as identical, diastereomer or enontiomer. [4 Marks]

i) CH3 H3C ii)H3CyH Br Br

andH CH3 H3C

0CH2CH3

H3C CA B

(c) Identify the following molecules as chiral or achiral.

HS''''''''O-SH Cf::'~ g:{,A B C

14

and no CH3

D

[2 marks]

CH3

H OH

H SH

CH3

0

6. (a) (i) Draw trans-l ,3-dimethylcyclohexane in its two chair conformations, and determine whether the two

chairs are identical, enantiomers or diastereomers. [3 Marks]

(ii) Calculate the enthalpy (relative energy) difference between the two chair conformations of cis-I,3-

dimethylcyclohexane (considering entropy change is zero). [axial MelH interaction: 3.75 kJ mol"; axial Me/Me

interaction: 15.5 kJ mol'] [3 Marks]

(b) Draw the two possible conformations of furfural. Indicate the correct conformer having more dipole momentwith justification. [1+2 Marks]

()--CHOFurfural

(c) Draw the most stable conformations of the following compounds. Predict the rate of saponification reactionof the following acetates with justification. [3 marks]

(i) M~~COOCH3Me

17

7. (a) For the following two reactions, how many isomers will be formed in each reaction and draw theirstructures? Will all the products be individually enantiomerically pure or racemic? Indicate the reaction pathwayfor each of the reaction? Explain the stereo-chemical outcome in few words. [3 + 1 + 1+1 Marks]

MeC2HsOH: H20 = 1:10

solvolysis

(i)B~ Me

? (ii) ?substitution

((2S,4S)-2-bromo-4-methylhexan-2-yl)benzene

(2S,4S)-2-bromo-4-methylhexane

(b) Why compound A reacts faster by the SN2 mechanism than the compound B when subjected to NaIseparately. Provide logical explanation of their relative rate differences? [3 Marks]

(c) For the following reaction, why alkene A form predominantly over alkene B? Explain with properconformational analysis. What are the structures of C and D which usually form as minor products during thisreaction? [3+1+1 Marks]

NaOEt

~Br

~+

Amajor

~ B+ c + o

minor

20

8. (a) Predict the structure of compounds A and B with relative stereochemistry. Explain the outcome in termsof elctrocyclization reaction. [3+3 Marks]

heatA

heatB

A monocyclicdiol

A bicyclic diol

(b) The following products are obtained after Diels-Alder cycloaddition reaction. Identify the diene anddienophile components for the individual cycloadducts? [O.5x6 == 3 Marks]

i) ii) o

oj iii) ,.-~

V-{

(c) In the following anionic oxy-Cope rearrangement identify the final product with stereochemistry? (Applyyour knowledge in conformational analysis) [3 Marks]

OH

~

KH, heata ten membered ketone(with unsaturation in the ring)

23

SPACE FOR ROUGH WORK

26

SPACE FOR ROUGH WORK

27

SPACE FOR ROUGH WORK

28