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Sodium borohydride is soluble in protic solvents such as water and lower alcohols. It also reacts with these protic solvents to produce H 2; however, these reactions are fairly slow. Complete decomposition of a methanol solution requires nearly 90 min at 20 °C. [11] It decomposes in neutral or acidic aqueous solutions, but is stable at pH 14. [9]
At low pH values, it efficiently reduces aldehydes and ketones. [7] As the pH increases, the reduction rate slows and instead, the imine intermediate becomes preferential for reduction. [ 7 ] For this reason, NaBH 3 CN is an ideal reducing agent for one-pot direct reductive amination reactions that don't isolate the intermediate imine.
To selectively form the allyl alcohol and avoid the 1,4 product, the Luche reduction uses "cerium borohydride" generated in situ from NaBH 4 and CeCl 3 (H 2 O) 7 [21] [22] The hydride source Zn(BH 4) 2 also shows 1,2 selectivity, as well as greater diastereoselectivity. It does so by coordinating not only to the carbonyl oxygen but also to ...
The values below are standard apparent reduction potentials (E°') for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution. [1] [2] The actual physiological potential depends on the ratio of the reduced (Red) and oxidized (Ox) forms according to the Nernst equation and the thermal voltage.
Since sodium cyanoborohydride is a mild reducing agent, it gives good chemoselectivity for reaction with certain functional groups in the presence of others. For example, sodium cyanoborohydride is generally incapable of reducing amides, ethers, esters and lactones, nitriles, or epoxides. [8]
In the reaction below, sodium tetraphenylborate allows N 2 to displace the chloride ligand, which is removed from solution as a precipitate of sodium chloride: FeHCl(diphosphine) 2 + NaB(C 6 H 5) 4 + N 2 → [FeH(N 2)(diphosphine) 2]B(C 6 H 5) 4 + NaCl. The use of tetraphenylborate is limited to non-acidic cations.
2 R-C≡N + 4 H 2 → (R-CH 2) 2 NH + NH 3 3 R-C≡N + 6 H 2 → (R-CH 2) 3 N + 2 NH 3. Such reactions proceed via enamine intermediates. [8] The most important reaction condition for selective primary amine production is catalyst choice. [1] Other important factors include solvent choice, solution pH, steric effects, temperature, and the ...
CaCO 3 + 2 H + ⇌ Ca 2+ + CO 2 + H 2 O. shows that pH will be related to calcium ion concentration, with lower pH going with higher calcium ion concentration. In this case, the higher the pH, the more bicarbonate and carbonate ion there will be, in contrast to the paradoxical situation described above, where one does not have equilibrium with ...