INDIAN INSTITUTEOF TECHNOLOGY, KHARAGPUREnd-Spring Semester 2017 -18

Date of Examination: _24-04-2018 _ Session (FN/AN) _AN_ Duration 3 hrs

Subject No.: CY41014Chemistry,

Subject Name: Principles of Organometallic and BioinorganicMaximum Marks: 100

Department/Center/School: Chemistry ----'--__

Specific charts, graph paper, log book etc., required: No _

Special Instructions: Please use Jst half of the answer script for 'Part A' and rest for 'Part B'.

Part A: Organometallics

Answer all the questions.

1. (a) Write down the products for the following reactions with justification.

. CD3 cooc"",l/Mn

oc/ I 'coco

6

?

co=. I/coW

oc/ I "'--coco

PhLi? ?

? (organometallic compound)

?

:l+rtJ( /CH3

Ta~ "'--CH

3

(b) What is the expected product of the following reaction? Give plausible mechanism.reagent to perform the reverse reaction from the product.

MeO ?

Suggest a 4

Ph3C+BF4-

[115-Cp(CO)2Fe(CHMeCH2Me)] ??

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2. (a) Write the mechanism for the following transformation and identify each step. 4

(b) Write a plausible mechanism for this transformation indicating the type of reaction for the each 6elementary step.

3. (a) Fluorene, a polycyclic organic compound, forms an ionic organometallic compound with a ["s_ 4CpFe] fragment and obeys the 18e rule. It has the molecular formula [(CsHs)Fe(CI3HIO)t[PF6r(A). Treatment of A with a base results in another 18e organometallic complex B with theformula [(CsHs)Fe(C13H9)]. Draw the reasonable structures of the complexes A and B.

(b) Predict the products and give reason for the difference in reactivity showing appropriate 4mechanism.

(c) Considering the associative substitution mechanism which among the following reaction will be 2faster? tCf

Co/\oc co

fCo/ \oc co

~Co/\

OC PPh3

fCo/ \

OC PPh3

4. (a) Between [("s-Cp)Mn(CO)3] and [("s-Cp2)Fe], which will undergo electrophilic substitution 2reaction faster? Give reason.

(b) Give reason for the difference in bond length in free and coordinated 1,3-butadiene. Show the 4appropriate orbital overlap.

)45pm

136 pm

~ ~'45pmZr- 140pm

~//

2

(c) Write down the expected product(s) if you treat the dicyclopentadiene with the Grubbs' first 4generation catalyst. Show the plausible mechanism.

nko5. (a) Show the difference in bonding between Fischer and Shrock Carbenes with the help of orbital 4

interaction. In which case the M=C bond will be shorter, and why?

(b) Predict the products (chiral ferrocene based ligands). Assign the chirality descriptor (RiS 6notation).

MerNMe2~ .

R2PH

AcOH

n-BuLi

PPh2CI??

Part B: Bioinorganic

Answer all the questions (1 to 9)

Answer all FIVE parts of Ql

1. Identify and write the single correct answer in the following (a-e).

a) Isomorphous replacement of Zn2+ center in HCA II is useful to probe the nature of the active s}te in the Zn2+based metalloenzymes in absence of X-ray crystallographic techniques. In one case the replacement retained50% of its activity. The most appropriate metal ion for this purpose is(A) Cu2+ (B) C02+ (C) Co3+ (D) Ni2+

b) The estimated pKa value of bound water molecule in [LZn(H20)]2+ (where L = tris-3-tert-butyl-5-methyl

pyrazolyl borate) is .

(A) 12.2 ± 0.1 (B) 7.0 ± 0.2 (C) 10.6 ± 0.2 (D) 3.5 ± 0.1

c) At room temperature reaction of TACN (l ,4,7 -triazacyclononane) with ferric acetate in aqueous MeOH gives(where OAc = acetete)(A) [Fe20(OAc)2(TACN)2f+ (B) [Fe20(OH)(OAc)(TACN)2]3+

(d) Within the active site structure of oxy-hemocyanain (oxy-Hc), the number of Cu-O and Cu-N bondspresent respectively, are(A) 4, 6 (B) 6, 4 (C) 2,6 (D) 4, 4

(e) The first metallobiomolecule discovered to carry Zn2+ ion at its active site is

(A) HCA II (B) CPA (C) LDH (D) Thermolysin

3

~---------------------------------------------- - -

·.

2. Within SOD I explain the role of Zn2+ ion in your own words and understanding.

[2 x 5]

[4]

3. In terms of ligand donor atoms available from amino acid residues for metal ion coordination, compare thecatalytically active active sites in carboxypeptidase A and ~-Iactamase.

[6]4. Explain the active site structure of methanemonoxygenase (MMO) in terms of bridging and terminalligands. [4]5. Identify and explain the following plot and discuss in your own words the Bohr effect and cooperativity forreversible binding of 02. [6]

20 Partiol presson:-in lcags

20 40 (/J 80 1((1 120 140Partial pressure 02 (mmt

6. HCA II found in red blood cells catalyzes, with a high turnover rate, the reversible hydration of CO2. With ageneral mechanistic profile explain the catalytic reaction from the participation of His-64 as proton acceptor.

[6]7. What are metalloenzyme inhibitors? What is Diamox? [4]

8. What is EC number? Explain the number 3.4.17. [4]

9. Explain the role of the metal ion center and function of metalloexopeptidase. With a neat schematic diagram,indicate the individual role of Tyr-248, hydrophobic pocket and salt bridge formation for peptidase activity.

[6]

Your question paper ends here

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