Hydrogen bonding nitrocompounds

HYDROGEN BONDING OF NITROCOMPOUNDS WITH SULPHURIC ACID... 

RNOa + HsSO RNO, HOSO3H RNQ2H+ + HS04-which have been obtained in the crystalline phase (Part I), affects these liquid phase properties to various degrees, depending upon the stability of the addition compounds, which is the result of the basicity of the mononitrocompounds (Gillespie and Solomons J. Chcm. /She. 1957 1796). In order to explain some peculiarities, however, the disruption of the hydrogen bonded structure of sulphuric acid by the presence of the molecules of the nitrocompounds in the mixtures must be taken into account also. 

In order to discuss the meaning of these viscosity isotherms we are going to apply the ideas about the viscosity of binary systems developed by one of us elsewhere [3] and to make use of the known data about the ionizations of these nitrocompounds in sulphuric acid [-5, 6], The viscosity isotherm of the system with nitromethane, showing strong negative deviations from additivity, does not necessarily mean that nitromethane does not interact with sulphuric acid in the sense of hydrogen bond formation and basic ionization. Cryoscopic investigations have shown that nitromethane ionizes as a weak base in sulphuric... 

Regarding the hydroxylation of nitroolefins, the reaction is performed under hydrogen-bonding catalysis using quinine-derived thiourea 170 (5 mol%), ethyl glyoxylate oxime as nucleophile in toluene at -24°C [374], This process, which constitutes a valid alternative to the Henry reaction, yields the corresponding hydroxylated nitrocompounds in good yields (63-83%) and enantioselectivities (48-93% ee) from ahphatic electrophiles (styrene derivatives are prone to retio-Michael addition) and has been successfully employed in the synthesis of optically active P-amino alcohols (Scheme 2.132) [375]. 

Though the hydrogenation of the double bond is one of the basic catalytic reactions in Pd chemistry, httle has been published on aqueous variants of this process. Hydrogenation of o ,j8-unsaturated aldehydes in recyclable biphasic systems in the presence of TPPTS complex of palladium has been studied. - Also, a biphasic hydrogenation of nitrocompounds in the presence of PdCla and TPPTS under mild conditions has been reported. Room temperature homocoupling of aryl iodides was achieved in neat water or water-acetone mixture in the presence of Pd/C or Pd(OAc)2, and Zn dust (Scheme 87). The addition of 18-crown-6 was required for the reaction in neat water. The reactions are run under aerobic conditions. The effect of phosphine is negative. - ... 

The radical-anions of aliphatic nitrocompounds are detectable in aqueous solution as transient intermediates formed during continuous electrolysis in the cavity of the esr spectrometer [4], Decay of the species occurs by protonation and then further reactions. 2-Methyl-2-nitropropane has no acidic hydrogens so that it can be examined in aqueous alkaline solution where the radical-anion is not protonated. Over the pH range 9-11, this radical-anion decays by a first order process with k = 0.8 0.1 s at 26 C. Decay results from cleavage of the carbon-nitrogen bond to give a carbon centred radical and nitrite ion. Ultimately, the di-(ferr,-butyI)nitrone radical is formed in follow-up reactions [5],... 

When a new carbon-carbon bond is produced by nucleophilic addition to conjugated systems, the process is called Michael addition. The generalised process involves an a, b-unsaturated compound and a compound containing an active hydrogen attached to a carbon atom (e.g., malonic ester, acetoacetic ester, nitrocompounds, aldehydes, ketones etc.) These are condensed in the presence of a base. The overall reaction and its mechanism can be represented as follows ... 

Silica gel-supported, cyclized polyacrylonitrile metal complexes as well as PMAA-Pd and PMAA-Pt complexes were prepared by copolymerization of MAA and a mixture of m- and p-DVB in the presence of silica gel [131]. The catalytic activity of the obtained complexes was examined in the reaction of cumene and ethylbenzene hydrogenation [131] and in the hydrogenation of aromatic and aliphatic nitrocompounds, alkenes and aliphatic aldehydes. Based on the decrease in the bond energy of Cu2p3/2 from 935 to 932.4 eV and the increase in the bond energy of Ajs from 399 to 399.6 eV, it was found, by XPS, that Cu is bound to a complex through a nitrogen atom of PAN. 

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