Experiment 3, page 4

Spillage & disposal:

Clear area, shut off all sources of ignition. Wear goggles, gloves, and laboratory coat.
Mop up with plenty of water and run to waste. Organise effective ventilation and
evaporate residual liquid.

Experimental Procedure

Preliminaries
1.Obtain dioxane (pre-dried over sodium, 20ml) from the bottle provided(DO NOT
ATTEMPT TO DRY THE SOLVENT WITH SODIUM YOURSELF!!!) in
a pre-dried flask.
2.Establish a t.l.c. system for the β-lactam ester 1to give an Rfvalue between 0.2 and
0.3. Use a mixtures of ethyl acetate and dichloromethane. The spots can be visualised
under the u.v. lamp and by placing the plates in a jar containing a few crystals of
iodine.
3.Record and interpret the i.r. spectrum of the penicillin; interpret the nmr spectrum of
the penicillin (provided).

Rearrangement of Penicillin V β-Sulphoxide 1.
In a 25ml round bottomed 2 or 3 neckedflask, dissolve dry pyridine (10μl) and 85%
orthophosphoric acid (14μl) in dry redistilled dioxan (see above) (10ml). Measure the acid and
base using a Gilson micropipette with a new tipfor each reagent. Add the penicillin ester 1
(0.50g) as provided, and heat the mixture to reflux overnight under nitrogen (CARE: check all

joints). Before commencing heating, flush the flask with N 2 and subsequently maintain a slight
positive pressure of N 2 applied to the top of the condenser, via a T-piece with a liquid paraffin
bubbler (see Demonstrator / Technician for details). Do not purge the system continuously with

N2since this will evaporate the solvent. Allow the solution to cool. Recheck the t.l.c. If necessary,
adjust the solvent composition (to x% EtOAc/DCM) to give an RFof ~ 0.5 for the product.

Flash Chromatography and Isolation of the Product

IMPORTANT!!!! SAFETY NOTE: Silica gel is dangerous by inhalation. Handle
the dry silica in a fume hood. Once slurried, the material can be used on the
bench provided it is not allowed to run dry. Dispose of all silica residues in the
bin provided.

Cover the sintered glass column with the plastic safety webbing provided and clampit vertically
over a conical flask. IN A FUME HOOD, slurry BDH flash chromatography silica (12g) in a
conical flask with dichloromethane (DCM). Pour the slurry intothe column and wash in the
residue with more DCM. Using the hand bellows, force the DCM through the column and thus
compact the silica. It is essential that the level of solvent is not forced beyond the top of the silica
otherwise channels will form in the silica and its effectiveness destroyed. The surface of the silica
pad mustbe as flat as possible. With extreme care, add more DCM to the column; do not disturb
the silica surface. Pouring the solvent carefully down the side of the column over the blade of a
wide spatula is helpful. Again, force the solvent through the column so that the surface of the silica
is just damp with DCM. If cracking or channelling occurs, repack the column..
Evaporate the dioxan solution containing the product to complete dryness. dissolve the residue in
the minimumvolume of DCM and carefully apply dropwise to the surface of the silica. Wash on
the last traces with a further small volume of DCM. Using the bellows, carefully force the liquid