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Reactions between aldimines and α-methylene carbonyls are also considered Mannich reactions because these imines form between amines and aldehydes. The reaction is named after Carl Mannich. [2] [3] Scheme 1 – Ammonia or an amine reacts with formaldehyde and an alpha acidic proton of a carbonyl compound to a beta amino carbonyl compound.
The reaction is generally performed in an aqueous solution at close to boiling. The first methylation of the amine begins with imine formation with formaldehyde. The formic acid acts as a source of hydride and reduces the imine to a secondary amine. Loss of carbon dioxide gas renders the reaction irreversible. Despite being more hindered, the ...
Formaldehyde is readily oxidized by atmospheric oxygen into formic acid. For this reason, commercial formaldehyde is typically contaminated with formic acid. Formaldehyde can be hydrogenated into methanol. In the Cannizzaro reaction, formaldehyde and base react to produce formic acid and methanol, a disproportionation reaction.
Halogenation of saturated hydrocarbons is a substitution reaction. The reaction typically involves free radical pathways. The regiochemistry of the halogenation of alkanes is largely determined by the relative weakness of the C–H bonds. This trend is reflected by the faster reaction at tertiary and secondary positions.
The direct reaction between phenol and paraformaldehyde is possible via the Casiraghi formylation, [4] but other methods apply masked forms of formaldehyde, in part to limit the formation of phenol formaldehyde resins. Aldehydes are strongly deactivating and as such phenols typically only react once.
The Blanc chloromethylation (also called the Blanc reaction) is the chemical reaction of aromatic rings with formaldehyde and hydrogen chloride to form chloromethyl arenes. The reaction is catalyzed by Lewis acids such as zinc chloride. [1] The reaction was discovered by Gustave Louis Blanc (1872-1927) in 1923. [2] [3] Blanc chloromethylation
Z must be powerful enough to facilitate deprotonation to the enolate ion even with a mild base. Using a strong base in this reaction would induce self-condensation of the aldehyde or ketone. The Hantzsch pyridine synthesis, the Gewald reaction and the Feist–Benary furan synthesis all contain a Knoevenagel
Gas stoichiometry is the quantitative relationship (ratio) between reactants and products in a chemical reaction with reactions that produce gases. Gas stoichiometry applies when the gases produced are assumed to be ideal, and the temperature, pressure, and volume of the gases are all known. The ideal gas law is used for these calculations.