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Under acidic conditions, the hemiacetal and the alcohol can further react to form an acetal and water. Simple hemiacetals are usually unstable, although cyclic ones such as glucose can be stable. Acetals are stable, but revert to the aldehyde in the presence of acid. Aldehydes can react with water to form hydrates, R−CH(OH) 2.
The two R' groups can be equivalent to each other (a "symmetric acetal") or not (a "mixed acetal"). Acetals are formed from and convertible to aldehydes or ketones and have the same oxidation state at the central carbon, but have substantially different chemical stability and reactivity as compared to the analogous carbonyl compounds.
The product, CH 3 CH(OCH 2 CH 3) 2, is formally named 1,1-diethoxyethane but is commonly referred to as "acetal". [39] This can cause confusion as "acetal" is more commonly used to describe compounds with the functional groups RCH(OR') 2 or RR'C(OR'') 2 rather than referring to this specific compound — in fact, 1,1-diethoxyethane is also ...
Besides the O,O-acetals, the S,O- and S,S-acetals also have an application, albeit scant, as carbonyl protecting groups too. Thiols , which one begins with to form these acetals, have a very unpleasant stench and are poisonous, which severely limit their applications.
It forms acetals readily, a prominent one being the spirocycle derived from pentaerythritol, diallylidene pentaerythritol. Acrolein participates in many Diels-Alder reactions, even with itself. Via Diels-Alder reactions, it is a precursor to some commercial fragrances, including myrac aldehyde ("lyral") and norbornene-2-carboxaldehyde. [5]
Hemiacetals form in the reaction between alcohols and aldehydes or ketones. Using an acid catalyst, the reaction proceeds via nucleophilic attack of the carbonyl group by the alcohol. [ 4 ] A subsequent nucleophilic attack of the hemiacetal by the alcohol results in an acetal . [ 2 ]
Phenylacetaldehyde is an aldehyde that consists of acetaldehyde bearing a phenyl substituent; the parent member of the phenylacetaldehyde class of compounds. It has a role as a human metabolite, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite. It is an alpha-CH2-containing aldehyde and a member of ...
In the presence of acid, hemiacetals can undergo an elimination reaction, losing the oxygen atom that once belonged to the parent aldehyde’s carbonyl group. These oxonium ions are powerful electrophiles, and react rapidly with a second molecule of alcohol to form new, stable compounds, called acetals.