Attempt to identify the compound A and the natural product N.

Warning: Care must be exercised when handling and working with the 'unknown' compounds. As a sensible precaution, assume them to be hazardous (many are) and avoid any skin contact, inhalation of vapour or ingestion.

Compound A

i. Purify the material by distillation and/or recrystallisation. Record the m.p. or, if liquid, the b.p. and the refractive index.

ii. Record the i.r., n.m.r. and u.v. spectra.

iii. Submit a sample of your purified compound for microanalysis. The submission forms are available at the service counter. Completed forms, to which a small polytop sample vial containing a few mgs. of your unknown A is attached, should be handed in via Nick Davies. The form will be returned to you (after 1-2 weeks) with the correct percentage composition figures and the molecular weight inserted. You will be assessed upon the accuracy of your results.

iv. Analyse the physical, spectral and microanalytical data in order to arrive at a structure for the unknown.

v. If at this stage, the identity of the compound is still uncertain, it will be necessary to make a suitable derivative (~100mg). Your data will have produced alternative structures so choose a derivative which you know will distinguish between these.

As a safety precaution, discuss the synthesis of the derivative with Dr. Marsden or Dr. Rzepa before proceding. If necessary, a COSHH assessment will have to be made.

vi. Propose a structure for A, citing literature data in corroboration.

Compound N

A sample of a natural product (or a simple derivative thereof) is provided together with its mass spectrum and an accurate mass measurement of the M+. (Occasionally, no M+ is observed. You will be told if this is the case and the mass difference from the M+ given).

All the natural products are well-known compounds that can be found in the literature. Remember that the samples provided are not analytically pure and that they could be unstable or poisonous.

i. Purify the sample if possible or appropriate (this is not always possible because of a high b.p. or lack of solubility).

ii. Record the m.p. or b.p., refractive index, the optical rotation, and the i.r. n.m.r. and u.v. spectra.

iii. From the accurate mass measurement of the M+, calculate the molecular formula. Interpret, as far as possible, all spectral data. This data can be used in conjuction with a search of the Beilstein database.

iv. If at this stage, the identity is still not clear, make a suitable derivative. As before, discuss the synthesis of the derivative with Dr. Marsden or Dr. Rzepa before proceeding. If necessary, a COSHH assessment will again have to be made. Collect the necessary physical/spectral data on the derivative, as before.

v. On the basis of this information and any relevant data from the literature, propose a structure for N.

Write Up

Write a succinct account of your observations and deductions for the structures of A and N. The write up should conform to a J. Chem. Soc., Perkin Trans. I, style (see notice board for details or see Issue 1, 1997, page v) and include all literature references. Hand in the account, including all spectra, together with any derivatives and any unused material. Do not mark the mass spectra provided.

(Accurate masses: 12C = 12.000000; 1H = 1.007824; 14N = 14.003074; 16O = 15.994914; 32S = 31.972072)

Copyright (c) H. S. Rzepa and ICSTM Chemistry Department, 1994-1997.