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Bromoaromatics are ubiquitous in chemistry, and their manufacture is often wasteful. Halogen exchange under hydrothermal conditions constitutes a viable alternative for their synthesis in some cases. The preparation of 1,2-dibromobenzene and 1-bromo-2-chlorobenzene from 1,2-dichlorobenzene, by treatment with hydrobromic acid in hydrothermal media at temperatures ranging from 240˚C to 320˚C was investigated as a viable alternative to de novo synthesis. The effects of temperature, exchange duration and the presence of Fe 3+ salts on product yields are discussed. Yields for both targeted haloarenes of up to 37% and 48%, respectively, were achieved, with very limited formation of 1,3-and 1,4-dihalobenzene isomers. A mechanism for halogen exchange was proposed.

We report first the complete study of the reactions of [CpMo(CO)2]2 (Mo≡Mo) (1, Cp = η5-C5H5) with salt-free phosphorus ylides Ph3P=CHR (2, Ph = C6H5; R = H (2a), CH3 (2b), C3H7 (2c), C6H5 (2d)) and with the Nal-adducts of the ylides Ph3P=CMe2 (Me = CH3), PhMe2P=CH2 and (PhO)3P=CH2. With 2, products of the type Cp(CO)2LMo-MoL(CO)2Cp (7, L = ylide) were obtained, and the salt adducts gave addition compounds of the type Cp(CO)2LMo-MoL(CO)2Cp-2NaI (12, L = ylide). These very reactive products represent novel bisphosphonioalkyl complexes, and were characterized by IR, mass and 1H NMR spectrometry. The reaction of 1 with hexaphenylcarbodiphosphorane, C(PPh3)2, leads to a novel double addition product, Cp2Mo2(CO)4[C(PPh3)2]2 (14). Some reactions of compounds 7, 12 and 14 were also studied; 7d (L = CHPh -PPh3) reacts with NaNH2 yielding ammonia and the disodium salt of the novel dianionic complex [CpMo(CO)2(CPh-PPh3)]22- (15); 7a (L = CH2-PPh3) reacts with CH3I forming CpMo(CO)3CH3 and traces of CpMo(CO)2(PPh3)I; all compounds of types 7,12 and 14 react with adsorbents (Silica-gel, Al2O3, etc.); thus chromatography is impossible, even under strict protection from air and humidity. A study of the processes occurring during chromatography under various conditions and the resulting products are also reported and discussed. [CpW(CO)3]2 (18) reacts with 2a forming also a bisphosphonioalkyl complex [CpW(CO)2L]2(L = CH2=PPh3); in this case, the ylide substitutes two carbonyl groups in 18. The compounds [Cp*M(CO)2]2 (M≡M) (Cp* = C5Me5 ; M = Cr, W) apparently do not react with phosphorous ylides; the corresponding Mo compound, [Cp*Mo(CO)2]2 , does react, but only the new mono-nuclear complex Cp*Mo(CO)2(PPh3)Cl (22) could be isolated.

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Treatment of homo- and heterocyclic aromatic substrates with basic deuterium oxide under near- or supercritical conditions results in rapid base-catalyzed hydrogen–deuterium exchange (HDE) in aromatic and benzylic positions. It has been postulated that HDE follows a simple deprotonation–reprotonation mechanism, but little evidence has been provided to date. This study correlates experimentally observed proton exchanges in n-butylbenzene with ab initio calculations of the acidities and potential energy (PE) profiles. In addition to providing further support for carbanion intermediacy in HDE, these results offer new insights into substrate acidities in near- and supercritical aqueous media and the optimal conditions required for their isotope exchange.