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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]
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]
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.
Since, aldehydes reduce more easily than ketones, they require milder reagents and milder conditions. At the other extreme, carboxylic acids, amides, and esters are poorly electrophilic and require strong reducing agents. [17] The idealized equation for the reduction of a ketone by sodium borohydride is: 4 RCOR' + NaBH 4 → NaB(OCHRR') 4
The complex is commercially available but can also be generated by the dissolution of diborane in THF. Alternatively, it can be prepared by the oxidation of sodium borohydride with iodine in THF. [2] The complex can reduce carboxylic acids to alcohols and is a common route for the reduction of amino acids to amino alcohols [3] (e.g. valinol).
Sodium borohydride and lithium aluminium hydride are commonly used for the reduction of organic compounds. [ 3 ] [ 4 ] These two reagents are on the extremes of reactivity—whereas lithium aluminium hydride reacts with nearly all reducible functional groups, sodium borohydride reacts with a much more limited range of functional groups .
In aqueous solutions, redox potential is a measure of the tendency of the solution to either gain or lose electrons in a reaction. A solution with a higher (more positive) reduction potential than some other molecule will have a tendency to gain electrons from this molecule (i.e. to be reduced by oxidizing this other molecule) and a solution with a lower (more negative) reduction potential ...
A buffer solution is a solution where the pH does not change significantly on dilution or if an acid or base is added at constant temperature. [1] Its pH changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical ...