Dibal-h reduction procedure

The mechanism for reduction by DIBAL is a little bit unusual compared to NaBH4. Whereas NaBH4 is considered a “nucleophilic” reductant – that is, it delivers hydride (H-) directly to a carbonyl carbon, DIBAL is an “electrophilic” reductant. That is, the first step in the reaction is coordination of a lone pair from the carbonyl oxygen (a nucleophile) to the aluminum (electrophile). It is only after coordinating to its carbonyl host that DIBAL delivers its hydride to the carbonyl carbon, resulting in formation of a neutral hemiacetal intermediate that is stable at low temperatures. Quenching of the reaction then breaks down the hemiacetal, resulting in isolation of the aldehyde. ( “real life” disclaimer :  this reaction looks great on paper but can sometimes be difficult to achieve in practice).

Of all aldehydes, formaldehyde is produced on the largest scale, about 6,000,000 tons per year. It is mainly used in the production of resins when combined with urea , melamine , and phenol (., Bakelite ). It is a precursor to methylene diphenyl diisocyanate ("MDI"), a precursor to polyurethanes . [10] The second main aldehyde is butyraldehyde , of which about 2,500,000 tons per year are prepared by hydroformylation . It is the principal precursor to 2-ethylhexanol , which is used as a plasticizer . [20] Acetaldehyde once was a dominating product, but production levels have declined to less than 1,000,000 tons per year because it mainly served as a precursor to acetic acid , which is now prepared by carbonylation of methanol . Many other aldehydes find commercial applications, often as precursors to alcohols, the so-called oxo alcohols , which are used in detergents. Some aldehydes are produced only on a small scale (less than 1000 tons per year) and are famously used as ingredients in flavours and perfumes such as N°5 from CHANEL . These include cinnamaldehyde and its derivatives, citral , and lilial .

Dibal-h reduction procedure

dibal-h reduction procedure

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