Q6(b). Three numericals
(i) Calculate the frequency of radiation required for a transition of J = 4 to J = 5 in the rotational spectrum of HCl. The rotational constant B = 10.6 cm⁻¹. (5 marks) (ii) The fundamental vibrational frequency of HCl is 2990 cm⁻¹. Calculate the fundamental vibrational frequency of DCl assuming the same bond strength. (5 marks) (iii) The molecular formula of a compound is C₃H₃N. The IR absorption frequencies are 1650 cm⁻¹, 2250 cm⁻¹ and 3100 cm⁻¹. Assign a structure for the compound. (5 marks)
Answer in brief
(i) 106 cm⁻¹, that is 3.18 × 10¹² Hz; (ii) DCl fundamental 2143 cm⁻¹; (iii) acrylonitrile, CH₂=CH–C≡N.
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Coversrotational transitionisotope shiftreduced massIR spectroscopyacrylonitrileHCl DCl
All parts of Question 6
- 6(a)(i) Products and intermediates of two reductions10 marks
- 6(a)(ii) Role of NMO in catalytic dihydroxylation5 marks
- 6(b) Three numericals15 marks
- 6(c)(i) Benzene to fulvene by light5 marks
- 6(c)(ii) Quantum yield of photobromination5 marks
- 6(c)(iii) Photolysis of 4,5-dimethylhexan-2-one5 marks
- 6(c)(iv) A, B and C from the mixed ketones5 marks