Chemistry UPSC PYQ 2018

Two substitution products result from the reaction of 3-chloro-3-methyl-1-butene with sodium acetate (CH3COO-Na+) in acetic acid under S_N1 conditions. Identify the products. Indicate the thermodynamic product and kinetic product.

(i) The commonly observed oxidation state of lanthanoids in aqueous solution is +3. - Comment. (ii) Calculate the effective magnetic moment of Ce^3+ (Z = 58) at room temperature.

Classify the following reaction and propose a suitable mechanism for it :

Explain the mechanism of free radical chain polymerization of vinyl chloride using benzoyl peroxide as an initiator.

The direct irradiation of either cis- or trans-stilbene at 313 nm results in the formation of a mixture of 93% cis- and 7% trans-olefin, no matter how long, within reason, the irradiation is continued. Give a suitable explanation for that.

How diborane can be synthesized industrially ? Draw the structure of diborane. Comment on the nature of boron-hydrogen bond present in it.

Answer the following : (i) How can you prepare 8-methylquinoline starting with o-toluidine as one of the starting materials? (ii) With suitable example, comment whether Fries rearrangement proceeds intermolecularly or intramolecularly. Give evidence in favour of your answer.

(i) Account for the fact that compound A is almost as strong an acid as H2SO4 :(ii) What happens when trans-2-butene is reacted with CH3COCl in presence of anhydrous AlCl3?

Answer the following briefly :(i) How can you prepare 8-methylquinoline starting with o-toluidine as one of the starting materials?(ii) With suitable example, comment whether Fries rearrangement proceeds intermolecularly or intramolecularly. Give evidence in favour of your answer.

(i) Predict the product of the following reactions with justification : (A) ClF + BF3 -> (B) ClF + CsF -> (C) CIF3 + BF3 -> (D) I2 + Br2 -> (ii) Determine the number of metal-metal bond(s) in [Re2Cl8]^(2-) (Z = 75) using simplified MO energy level diagram.

(i) Using the statement of First law of thermodynamics, argue upon the various effects on rising clouds as it goes to higher altitudes. (ii) If P1 = 3.00 atm, V1 = 500 cm^3 P2 = 1.00 atm, V2 = 2000 cm^3 Calculate the work, W_reversible for the processes shown in figure (a) and (b).

(i) Predict the product of the following reactions with justification : (A) ClF + BF₃ → (B) ClF + CsF → (C) ClF₃ + BF₃ → (D) I₂ - Br₂ → (ii) Determine the number of metal-metal bond(s) in [Re₂Cl₈]²⁻ (Z = 75) using simplified MO energy level diagram.

Calculate the internal energy, U when 1.00 mol of H2O goes from 25.0 °C and 1.00 atm to 30.0 °C and 1.00 atm. Densities of water are 0.9970 g/cm³ at 0 °C and 0.9956 g/cm³ at 100 °C.

Identify the products and draw the structure of A.

(i) What are crystal defects ? Give a brief account on stoichiometric defects. (ii) Explain the conduction mechanism in semiconductors.

(i) Distinguish between Galvanic cells and concentration cells with an example each. (ii) A silver nitrate solution containing 0.00739 gm of AgNO₃ per gm of water is electrolysed between silver electrodes. During the experiment 0.078 gm of Ag was deposited on the cathode. At the end of the experiment anode solution contained 23.14 gm of H₂O and 0.236 gm of AgNO₃. What is the transport number of Ag⁺ ? After electrolysis, the anode solution has (a) 23.14 gm water and (b) 0.236 gm silver nitrate.

(i) Distinguish between Galvanic cells and concentration cells with an example each. (ii) A silver nitrate solution containing 0.00739 gm of AgNO3 per gm of water is electrolysed between silver electrodes. During the experiment 0.078 gm of Ag was deposited on the cathode. At the end of the experiment anode solution contained 23.14 gm of H2O and 0.236 gm of AgNO3. What is the transport number of Ag^+ ? After electrolysis, the anode solution has (a) 23.14 gm water and (b) 0.236 gm AgNO3.

(i) Determine the geometry of [Ni(H2O)6]^(2+) (paramagnetic complex with two unpaired electrons) using valence bond theory. (ii) Using Orgel diagram, assign the absorption bands of [Ni(H2O)6]^(2+) at 8500, 13800 and 25300 cm^-1 in solution. Calculate the 10 Dq value.

The rate constant k1 for the reaction described by H^+(aq) + OH^-(aq) <=> H2O(l) is 1.4 x 10^11 dm^3.mol^-1.s^-1. Calculate the half life of the above reaction if the initial conditions are (i) [H^+]0 = [OH^-]0 = 0.10 mol.dm^-3 (ii) [H^+]0 = [OH^-]0 = 1.0 x 10^-7 mol.dm^-3

Draw diagrams showing the capillary action of (i) water and (ii) mercury in two glass tubes of different radii. Explain their behavior also.

Observe the following half cell reactions : (i) I2 + 2e^- -> 2I^- ; E^(theta) = +0.54 V (ii) 2Br^- -> Br2 + 2e^- ; E^(theta) = -1.09 V (iii) Fe -> Fe^(2+) + 2e^- ; E^(theta) = +0.44 V Using the above Standard Electrode Potential Values, explain the spontaneity or non-spontaneity for the following reactions : (A) Br2 + 2I^- -> 2Br^- + I2 (B) Fe + Br2 -> Fe^(2+) + 2Br^- (C) Fe + I2 -> Fe^(2+) + 2I^- (D) I2 + 2Br^- -> 2I^- + Br2

Which of the following known sigmatropic rearrangements would proceed readily and which slowly? Explain your answers :(i) CH3-CH=CD2 -> CH2=CH-CD2(ii) H-D -> H-D

Which of the following known sigmatropic rearrangements would proceed readily and which slowly? Explain your answers.

Draw the active site (coordination sphere only) of cytochrome C and cytochrome P-450. Discuss their biochemical function.

Consider the formation of MgO(s). Assume that Delta H_f(theta) and Delta S_f(theta) are independent of temperature. Mg(s) + 1/2 O2(g) -> MgO(s) Delta H_f(theta) = -602 kJ/mol Delta S_f(theta) = -108 J/K/mol (i) Calculate Delta G_f(theta) for the formation of MgO(s) at 0 C. Is this reaction spontaneous or non-spontaneous at 0 C. (ii) Is there a temperature at which formation of MgO switches from spontaneous to non-spontaneous or vice-versa ? If no, explain why not ? If yes, calculate the temperature at which the spontaneity of the reaction switches ?

Find out the ground state term symbol of Ho³⁺ (Z = 67).

How do the UV spectral data lambda_max 296 nm, epsilon_max 10700 and lambda_max 281 nm, epsilon_max 20800 help in deciding between structures X and Y?

How do you prepare the above isomers starting from [PtCl4]^(2-) using the concept of trans effect ? (Order of trans directing ability : Br^- > Cl^- > py > NH3)

By taking 1-methylcyclopentene as an example, explain hydroboration-oxidation reaction. Justify that it is stereoselective and regioselective.

The mass spectra of two different cycloalkanes both show a molecular ion peak at m/z = 98. One spectrum shows a base peak at m/z = 69 and the other shows a base peak at m/z = 83. Identify the two cycloalkanes.

(i) Distinguish fluorescence from phosphorescence. (ii) In the photobromination of cinnamic acid to dibromocinnamic acid using light of wavelength 4358 Å a light intensity of 14,000 ergs sec⁻¹ produced, and a decrease of 0.075 millimole of bromine during an exposure for 1105 sec. The solution absorbed 80-1% of the light passing through it. Calculate the quantum yield.

An organic compound (MF C6H10O) exhibits the following spectral characteristics : UV (lambda_max : 280 nm) IR (nu_max : 1715 cm^-1) 1H NMR (delta, ppm) : 0.90 (3H, t), 1.60 (2H, m), 2.20 (3H, s), 2.40 (2H, t) Mass (m/z) : 86, 71, 58, 43 (100%) Deduce the structure of the compound and explain the principal ions observed in the mass spectrum.

Draw all possible stereoisomers of [PtCl₂Br₂(NH₃)₂].

Outline the mechanism for the following reaction: In what way is NaBH4 different from LiAlH4 in 'chemoselectivity'?

When trans-4-tert-butylcyclohex-2-enol is reacted separately with mCPBA and V(acac)2 / tert-butylhydroperoxide, in the second reaction only one product is formed, whereas in the first case a mixture of two isomeric products is obtained. Write the structure of the product in each case with proper stereochemical outcome and justification.

(i) The commonly observed oxidation state of lanthanoids in aqueous solution is +3. Comment. (ii) Calculate the effective magnetic moment of Ce³⁺ (Z = 58) at room temperature.

(i) Determine the geometry of [Ni(H₂O)₆]²⁺ (paramagnetic complex with two unpaired electrons) using valence bond theory. (ii) Using Orgel diagram, assign the absorption bands of [Ni(H₂O)₆]²⁺ at 8500, 13800 and 25300 cm⁻¹ in solution. Calculate the 10 Dq value.

(i) Consider the reversible expansion of a perfect gas. Provide the physical interpretation for the fact PVɣ constant for an adiabatic change, whereas PV = constant for an isothermal change. (ii) What happens to the air temperature in a valley when cold air blowing from the mountain tops descends into the valley ?

(i) Draw the structure of the following complexes : (A) bis (eta^6-benzene) chromium (0) (B) fac-triaquatris (dimethylamine) cobalt (III) tetraoxosulfate (VI) (ii) Give IUPAC nomenclature of (A) Na[B(NO3)4] (B) [Co(NH3)6][CoCl6]

Arrange the following compounds in order of their decreasing reaction rate of substitution with aqueous formic acid and justify your answer :

Write the mechanism of the following:

Two substitution products result from the reaction of 3-chloro-3-methyl-1-butene with sodium acetate (CH3COO-Na+) in acetic acid under SN1 conditions. Identify the products. Indicate the thermodynamic product and kinetic product.

Each of PhCH2COCH2Cl and PhCHCICOCH3 in reaction with NaOMe/MeOH furnishes the same product. What mechanistic implication can be drawn from the above fact?

Explain the following on the basis of VBT and hybridization : (i) BeF2 is linear whereas SF2 is angular. (ii) P forms two chlorides PCl5 and PCl3 whereas N forms only one NCl3.

What is Birch reduction? Suggest its mechanism by taking a suitable example. Why does Birch reduction on benzene derivatives with an electron-donating group happen on ortho and meta positions?

A signal has been reported to occur at 120 Hz downfield from TMS in an NMR spectrometer with a 60 MHz operating frequency. (i) What is its chemical shift? (ii) What would its chemical shift be in an instrument operating at 100 MHz? (iii) How many hertz downfield from TMS would the signal be in a 100 MHz spectrometer?

Carry out the following transformations :(i)(ii)

Predict the product(s) with mechanism for the following :(i)(ii)(iii)

(i) Derive Bragg's equation. (ii) The potassium chloride crystal structure is like that of sodium chloride. The unit cell contains four potassium ions and four chloride ions. Given that the size of unit cell as 6.29 A and the density of potassium chloride as 1.99 g/c.c. Calculate the number of potassium ions and chloride ions in 1.00 g of the salt.

(i) One side of glass cylinder is initially filled with H₂ at a pressure P and other side with N₂ at a pressure 2P. This glass cylinder is closed at both ends and a glass filter in the middle of the cylinder divides it into two compartments of equal volume. Describe what happens, starting at time, t = 0 at constant temperature and assuming that the pores of filter have a diameter much smaller than the mean free paths of the gases. (ii) Account for the difference between vapour and gas on the basis of critical temperature.

An organic compound (MF C5H10O) exhibits the following spectral characteristics :UV (lambda max : 280 nm)IR v max : 1715 cm-11H NMR (delta, ppm) : 0.90 (3H, t), 1.60 (2H, m), 2.20 (3H, s), 2.40 (2H, t)Mass (m/z) : 86, 71, 58, 43 (100%) Deduce the structure of the compound and explain the principal ions observed in the mass spectrum.

Outline the mechanism of the following reaction : R-OH + i) LiAlH4 / ii) H2O -> R-OH 'In what way is NaBH4 different from LiAlH4 in 'chemoselectivity'?

Write the mechanism of the following :(i)(ii)(iii)

(i) Explain the significance of Kelvin equation. (ii) Discuss the effect of temperature on the viscosity of liquids and gases.

Calculate the bond order for the following molecules/ions. Arrange them as per the increasing order of their stability. Give reasons. (i) H2^+ (ii) Ne2 (iii) CN^- (iv) NO (v) HF

Write the product(s) with proper stereochemical outcome of acetolysis of each of threo- and erythro-3-phenyl-2-butyltosylate giving the reaction pathway in each case.

Consider the formation of MgO(s). Assume that ΔH% and ΔS% are independent of temperature. Mg(s) + &frac{1}{2}O₂(g) → MgO(s) ΔH% = -602 kJ/mol ΔS% = -108 J/K/mol (i) Calculate ΔG% for the formation of MgO(s) at 0 °C. Is this reaction spontaneous or non-spontaneous at 0 °C? (ii) Is there a temperature at which formation of MgO switches from spontaneous to non-spontaneous or vice-versa? If no, explain why not ? If yes, calculate the temperature at which the spontaneity of the reaction switches?

Distinguish between DNA and RNA with regard to their nucleotide structures, location in the cells and functions.

(i) Define and explain Einstein's law of photochemical equivalence. (ii) Discuss the photochemical reactions between hydrogen and chlorine.

(i) Consider the reversible expansion of a perfect gas. Provide the physical interpretation for the fact PV^gamma = constant for an adiabatic change, whereas PV = constant for an isothermal change. (ii) What happens to the air temperature in a valley when cold air blowing from the mountain tops descends into the valley ?

Distinguish between fluorescence emission and phosphorescence emission giving suitable examples.

Predict the product(s) with mechanism for the following:

(i) Derive Bragg's equation. (ii) The potassium chloride crystal structure is like that of sodium chloride. The unit cell contains four potassium ions and four chloride ions. Given that the size of unit cell as 6.29 Å and the density of potassium chloride as 1.99 g/c.c. Calculate the number of potassium ions and chloride ions in 1.00 g of the salt.

Observe the following half cell reactions : (i) I₂ + 2e⁻ → 2I⁻ ; E% = +0.54 V (ii) 2Br⁻ → Br₂ + 2e⁻ ; E% = -1.09 V (iii) Fe – → Fe²⁺ + 2e⁻ ; E% = +0.44 V Using the above Standard Electrode Potential Values, explain the spontaneity or non-spontaneity for the following reactions : (A) Br₂ - 2I⁻ → 2Br⁻ - I₂ (B) Fe + Br₂ → - Fe²⁺ + 2Br⁻ (C) Fe + I₂ → Fe²⁺ + 2I⁻ (D) I₂ - 2Br⁻ → 2I⁻ + Br₂

Find out the ground state term symbol of Ho^3+ (Z = 67).

(i) Using the statement of First law of thermodynamics, argue upon the various effects on rising clouds as it goes to higher altitudes. (ii) If P₁ = 3.00 atm V₁ = 500 cm³ P₂ = 1.00 atm V₂ = 2000 cm³ Calculate the work, W₂₅ reversible for the processes shown in figure (a) and (b).

How is NBS obtained from succinimide? Write its reaction with propene in presence of sunlight. Outline the mechanism.

Show that two phases are in thermal equilibrium only if their temperature are same.

Draw the pi-molecular orbital energy level diagram for the following: (i) Benzene (ii) Cyclobutadiene (iii) Cyclopentadienyl anion

Classify the following examples as aromatic, anti-aromatic or non-aromatic. Write their structures also :(i) Tetrahydrofuran(ii) Cyclooctatrienyl dianion(iii) Azulene(iv) Tropolone

Explain charge-transfer spectra by taking a suitable donor-acceptor type complex.

A particle in a rigid box of length 'L' is in its ground state. What is the probability of finding the particle in the centre half of the box ?

(i) Explain the effect of temperature on rate constant. (ii) In the hydrolysis of ethyl acetate using equal concentrations of ester and NaOH, the following results were obtained : Show that the reaction is of second order.

When trans-4-tert-butylcyclohex-2-en-1-ol is reacted separately with mCPBA and V(acac)2 / tert-butylhydroperoxide, in the second reaction only one product is formed, whereas in the first case a mixture of two isomeric products is obtained. Write the structure of the product in each case with proper stereochemical outcome and justification.

Each of PhCH2COCH2Cl and PhCHICOCH3 in reaction with NaOMe/MeOH furnishes the same product. What mechanistic implication can be drawn from the above fact?

What do you mean by secondary structure of proteins? Explain alpha-helix and beta-pleated sheet structures of proteins.

The rate constant k₁ for the reaction described by H⁺(aq) + OH⁻(aq) → H₂O(1) is 1.4×10¹¹ dm³ mol⁻¹ s⁻¹ Calculate the half life of the above reaction if the initial conditions are (i) [H⁺]₀ = [OH⁻]₀ = 0.10 mol dm⁻³ (ii) [H⁺]₀ = [OH⁻]₀ = 1.0×10⁻⁷ mol dm⁻³

Give the synthetic schemes including reaction conditions for the preparation of the following polymers from their monomers: (i) Nylon-66 (ii) Teflon (iii) Terylene

(i) Write BET equation. Explain the terms involved in it. How is it useful for the determination of surface area ? (ii) Explain the mechanism of reaction on heterogeneous catalysis.

(i) Distinguish fluorescence from phosphorescence. (ii) In the photobromination of cinnamic acid to dibromocinnamic acid using light of wavelength 4358 A at a light intensity of 14,000 ergs sec^-1 produced, and a decrease of 0.075 millimole of bromine during an exposure for 1105 sec. The solution absorbed 80-1% of the light passing through it. Calculate the quantum yield.

Write the structures of the products expected from hydroxylation of maleic acid and fumaric acid using OsO4 / Py, with the stereochemistry. What is the role of pyridine in the above reaction?

Which of the following conjugated dienes would not react with a dienophile in Diels-Alder reaction? Justify your answer :(i)(ii)(iii)(iv)(v)

Classify the following examples as aromatic, anti-aromatic or non-aromatic. Write their structures also : (i) Tetrahydrofuran (ii) Cyclooctatetraene dianion (iii) Azulene (iv) Tropolone

(i) What is an orbital and how is it related to the probability density ? (ii) Determine the number of radial nodes, angular nodes and total number of nodes in the following orbitals : 2p, 3s, 3p, 4d, 5f. (iii) Would it be possible to determine the position and momentum of an electron simultaneously and accurately if the value of Plank's constant is zero ?

Calculate the bond order for the following molecules/ions. Arrange them as per the increasing order of their stability. Give reasons. (i) H₂⁻ (ii) Ne₂ (iii) CN⁻ (iv) NO (v) HF

Calculate the internal energy, U when 1.00 mol of H2O goes from 25.0 C and 1.00 atm to 30.0 C and 1.00 atm. Densities of water are 0.9970 g/cm3 at 0 C and 0.9956 g/cm3 at 100 C.

Maleic anhydride reacts rapidly with 1,3-butadiene, but does not react at all with ethene under thermal conditions. Explain.

Which of the following conjugated dienes would not react with a dienophile in Diels-Alder reaction? Justify your answer.

Draw the active site structure of [2Fe-2S] and [4Fe-4S] ferredoxins. Comment on the oxidation state of metal in oxidised and reduced forms of [2Fe-2S].

Carry out the following transformations:

(i) One side of glass cylinder is initially filled with H2 at a pressure P and other side with N2 at a pressure 2P. This glass cylinder is closed at both ends and a glass filter in the middle of the cylinder divides it into two compartments of equal volume. Describe what happens, starting at time, t = 0 at constant temperature and assuming that the pores of filter have a diameter much smaller than the mean free paths of the gases. (ii) Account for the difference between vapour and gas on the basis of critical temperature.

How do you prepare the above isomers starting from [PtCl₄]²⁻ using the concept of trans effect ? (Order of trans directing ability : Br⁻ > Cl⁻ > py > NH₃)

Explain what inferences about the type of reaction and stereochemistry can be gained from the observation that when each of A and B undergoes reaction with KOH in methanol the rate of reaction is very slow for A compared with that of B :

Explain Langmuir adsorption isotherm (i) when the gas pressure 'P' is very small and (ii) when the gas pressure 'P' is very high.

(i) Explain why fusion curve of ice has negative slope whereas sublimation curve has positive slope in the phase diagram. (ii) Label and compare the phase diagrams given above :

Explain the conditions for the following reaction, very briefly describe the steps involved and comment if the reaction is reversible : + || ->

(i) Draw the structure of the following complexes : (A) bis (η⁶-benzene) chromium (0) (B) fac-triaquatris (dimethylamine) cobalt (III) tetraoxosulfate (VI) (ii) Give IUPAC nomenclature of (A) Na[B(NO₂)₄] (B) [Co(NH₃)₆][CoCl₆]

Explain the following on the basis of VBT and hybridization : (i) BeF₂ is linear whereas SF₂ is angular. (ii) P forms two chlorides PCl₃ and PCl₅ whereas N forms only one NCl₃.

Draw all possible stereoisomers of [PtCl2Br2(NH3)2].

Distinguish between HDPE and LDPE with reference to their mode of production and physical properties. Mention any two applications for each.