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Generic structure of acetals. In organic chemistry, an acetal is a functional group with the connectivity R 2 C(OR') 2.Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments not hydrogen.
In organic chemistry, an acetyl group is a functional group denoted by the chemical formula −COCH 3 and the structure −C(=O)−CH 3. It is sometimes represented by the symbol Ac [5] [6] (not to be confused with the element actinium). In IUPAC nomenclature, an acetyl group is called an ethanoyl group.
Condensation products from propenal and pentaerythritol were first described in 1950. [4] [5] The synthesis is carried using a general synthesis method for acetals at acid pH (pH 3-5) by reacting an alcohol with an excess of aldehyde, which is stabilized with hydroquinone in the case of propenal, which tends to polymerize at elevated temperature.
The latter reagent in itself is an acetal and therefore the reaction is actually a cross-acetalisation. Kinetic reaction control results from 2-methoxypropene as the reagent. D-ribose in itself is a hemiacetal and in equilibrium with the pyranose 3. In aqueous solution ribose is 75% pyranose and 25% furanose and a different acetal 4 is formed.
Acid catalyzed acetal formation from the corresponding hemiacetal. Acetals, as already pointed out, are stable tetrahedral intermediates so they can be used as protective groups in organic synthesis. Acetals are stable under basic conditions, so they can be used to protect ketones from a base. The acetal group is hydrolyzed under acidic conditions.
Polyoxymethylene (POM), also known as acetal, [4] polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts requiring high stiffness, low friction, and excellent dimensional stability.
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It is a reagent used in organic synthesis for the formation of methyl ethers. [3] The product of reaction of an aldehyde with trimethyl orthoformate is an acetal . In general cases, these acetals can be deprotected back to the aldehyde by using hydrochloric acid .