W.J. le Noble

Organic synthesis at high pressure

The recommendation is developed that all synthetic chemists should always consider pressure as one of the routine variables available to them, along with temperature, solvent, reaction time, catalysts, and so forth. Ideally, equipment should be available both in the 1–5 and 10–20 kbar range, the former for the habitual testing of all reaction steps under increased pressure, and the latter for the more unusual instances in which gigapascal pressures appear to force otherwise reluctant reactions. The hope is that synthetic chemists will learn to optimize yields and conversions with respect to pressure as well as the other variables, and to report the pressure used just as routinely as they report reaction times and temperatures now.

All quartz optical cell of constant diameter for use in high pressure studies

A simple optical cell is described for photochemical or spectrophotometric experiments under pressure. The cell, basically a syringe with optical windows at each end, is made entirely of quartz; the sample is not in contact with plastic or metal parts. Since the cylindrical sample space has a variable, self‐adjusting length and a constant diameter, no compressibility corrections are required.

Reduction of 5-p-anilinoadamantan-2-one. A reinvestigation

Abstract Revised data are reported which show that π-donor p -substituents in a phenyl ring located in the 5-position of adamantanone can moderate its ability m affect face selection, but cannot reverse it as claimed earlier.

Pressure effects in a [2+2] photocycloaddition and -reversion

Abstract Evidence is presented to support the conclusion that the [2+2] photocycloaddition of acrylonitrile to naphthalene has a late transition state similar in volume to those in concerted thermal cycloadditions.

Kinetics of Organic Reactions at High Pressure

With the privilege of participating as a repeater in this second Advanced Study Institute on High Pressure comes the duty not only to state one’s objectives, but also to outline the differences with the Chapters written for the earlier occasion. Both of those Chapters dealt with kinetics at high pressure, the first with “model reactions”1 and the other with “problem reactions”.2 The model reactions included, especially, protic acid base equilibria. The reaction volumes of large numbers of such equilibria are known, and these provide a wealth of information on which kinetic studies can be securely founded. However, the models also included a number of data on rate constants under pressure. The reactions discussed comprised those in which the mechanism is exceedingly simple and dominated by a single feature, and in which alternative studies had left essentially no doubt about the pathway. The second chapter described the application of knowledge thus gained, to reactions the mechanisms of which were still unsettled, or even controversial.

Ionization Volumes by Means of Direct Dilatometry

A rapid and convenient new technique is described to determine ionization volumes directly by means of dilatometry. In this method, acid and base solutions of appropriate strength are ‘stacked’ and mixed after an initial reading is made. Each solution is also treated similarly with solvent alone. The ionization volumes of water and of several weak acids and bases in water have been calculated from the data. They generally compare quite well with literature values determined by more elaborate means; several new results are also reported.

Organic Model Reactions Under Pressure

It is probably fair to say that the lectures given here to date have been concerned primarily with physics, and with the physical properties of compounds and sometimes mixtures; in contrast, my remarks and those of my colleagues to follow are almost exclusively directed at chemistry and chemical properties. It goes without saying, however, that the chemist who uses high pressure methodology depends very much indeed on the knowledge that has been gathered by the physicists and physical chemists.

Set mechanism in the lithium aluminum deuteride reduction of chloroadamantanes, and its induction by remote substituents

Abstract The title reduction may lead to very incomplete isotopic substitution as a result of SET intrusion and the related intermediacy of radicals and hydrogen abstraction from the solvent, even though the halogen to be replaced is chlorine. Two examples are reported. In one of them, this mechanism is shown to be induced through five single bonds by an ether substituent separated from the chlorine by a rigid W-chain of saturated carbons.

Stereospecific return in the methanolysis of propargylic halides. Remote phenyl directive effect on the stereoselection of carbonium ion capture

Abstract Product analysis in the methanolysis of an epimerie pair of propargyl chlorides shows that the solvolysis products arise from a common intermediate. The carbonium ion preferentially captures methanol on the Z -side by a 3:1 margin. The return products (the allenic isomers) are formed with complete retention.

The electronic factor in the face selection of iron tricarbonyl complexation

Abstract The iron tricarbonyl complexes of 1-(2-adamantylidine)-2-methylenecyclohexane and of the 5-fluroadamantylidene analog have been prepared. Both the syn and anti isomers were obtained in the latter case; the major product has the syn configuration as established by means of X-ray diffraction. The reaction therefore joins several others in which reagents of various types were added to a trigonal center C2 in a adamantanes carrying an electron withdrawing substituent at C5: this attack also, occurs preferentially at the zu face.