Ring stripping charge

Fig. 35. Disk and ring voltammograms recorded during the oxidation of thin-layer Co-Al electrodeposits from a Pt-RRDE in pure 60.0 m/o AlCl3-EtMeImCl melt. These deposits were produced with a charge density of 425 mC cm 2 in melt containing 5.00 mmol L-1 M Co(II) at the following deposition potentials (—) 0.200, (—) 0.100, and ( ) 0 V. During stripping, the disk electrode was scanned at 0.002 V s 1, and Er was held at 0.500 V. The angular velocity of the RRDE was 104.7 rad s 1. Adapted from Mitchell et al. [44] by permission of The Electrochemical Society.

The chemistry of mass-selected ionized halobenzenes toward ammonia in a quadrupole collision cell pointed out that the CA spectra of the m/z 94 ions, i.e. protonated aniline, prepared in each of these conditions are qualitatively similar, since all the fragmentations are common. The major observed differences concern the relative intensities of the peaks associated with charge stripping and ammonia loss. In this context, substituted benzenes protonated on a ring carbon atom are more prone to undergo double ionization than substituted benzenes protonated on a substituent. 

The first step in this transform comprises formation of a radical dianion (1-2) from reaction of at the sites of lowest electron density (Scheme 4.1). In the case of steroids, this requirement rules out all but positions 1,4 of the aromatic ring A. The charges on the intermediate then strip protons from the alcohol in the reaction medium to yield the dihydrobenzene 1-3. The alcohol, frequently tert-butanol, thus acts as a quench. The enol ether function in the product is sufficiently robust to serve as a protecting group in many subsequent reactions. Mild acid hydrolysis of that enol ether affords the surprisingly stable unconjugated ketone 1-4. Treatment of this last intermediate with mineral acid causes the unsaturation to move over into conjugation at C4 (1-5). 

Fig. 1. Schematic of the germanium strip detector used in this work. Crossed electrodes provide two-dimensional position localisation of interactions. The electrodes may be read out individually or grouped in two charge-division chains, one for each side, then readout with four channels of electronics (not shown here). The guard ring provides increased immunity to leakage currents. There are 5 strips on each face of the detector, centered on a 9 mm pitch and 45 mm long. The active volume is 45 X 45 X 12 mm.

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