CH437 ORGANIC STRUCTURAL ANALYSISEXAMINATION 2: Friday, 21 December 2007, 15.00 – 16.30

Attempt all the questions

1. The structure and 1H NMR spectrum of camphor are shown below.(a) When Signal K is irradiated, positive NOE enhancements are observed for A,

B and a negative enhancement occurs at D.(b) When I is irradiated, positive NOE enhancements are observed for B, C and

E.(c) Irradiation of signal A, gives medium NOE enhancements of B and K, and a

large enhancement at D.(d) Irradiation of C, gives NOE enhancements of B, G (large) and I.

Using the information above and any other information from the spectrum, assign as many protons as you can in the structure of camphor.

(6 points)

2. (i) Use the Woodward-Fieser rules to predict the UV maximum (max) for the * transition in the UV spectrum of (I). Show working.

CH3

O

(I) (2 points)

(ii) For each of the following, (a) – (b), state which have max values that are accurately predicted by the Woodward-Fieser rules. (E.g. answer (a) yes, (b) no…etc).

1

(a) (b)

O O

(c) (d) (2 points)

3 (i) Use Scott’s rules to predict max for the principal absorption band in the UV spectrum of (II). Show working.

O

OH

CH3O

O

HO

OCH3

(II) (III) (2 points)

(ii) Describe a method, using only UV spectroscopy and Scott’s rules, for distinguishing between (II) and (III). (2 points)

4. A diastereoisomer of 10-methyl-3-decalone (IV) exhibits a positive Cotton effect in its CD spectrum. Use the octant rule to establish the stereochemistry of (IV) (i.e. whether the ring fusion is cis or trans and whether H is or , according to the standard notation for steroids and related compounds).

CH3

HO

510

12

3

4 67

8

9

(4 points)

2

5. Use the spectra below to identify X07A, of molecular formula C10H10O2. Show working. (12 points)

FTIR

/cm-1

1H NMR spectrum (with expansion of region 6.40 – 10.00 ppm)

3

13C NMR and DEPT Spectra

/ppm

/ppm

COSY Spectrum

4