In organic chemistry, a hemiaminal (also carbinolamine) is a functional group or type of chemical compound that has a hydroxyl group and an amine attached to the same carbon atom: . R can be hydrogen or an alkyl group. Hemiaminals are intermediates in imine formation from an amine and a carbonyl by alkylimino-de-oxo-bisubstitution. Hemiaminals can be viewed as a blend of aminals and geminal diol. They are a special case of amino alcohols.
The adducts formed by the addition of ammonia to aldehydes have long been studied. Compounds containing both a primary amino group and a hydroxyl group bonded to the same carbon atom are rarely stable, as they tend to dehydrate to form imines which polymerise to hexamethylenetetramine. A rare stable example is the adduct of ammonia and hexafluoroacetone, .
The C-substituted derivatives are obtained by reaction of aldehydes and ammonia:
3 RCHO + 3 NH3 -> (RCHNH)3 + 3 H2O
N-substituted derivatives are somewhat stable. They are invoked but rarely observed as intermediates in the Mannich reaction. These N,N',N''-trisubstituted hexahydro-1,3,5-triazines arise from the condensation of the amine and formaldehyde as illustrated by the route to 1,3,5-trimethyl-1,3,5-triazacyclohexane:
3 CH2O + 3 H2NMe -> (CH2NMe)3 + 3 H2O
Although adducts generated from primary amines or ammonia are usually unstable, the hemiaminals have been trapped in a cavity.
One of the simplest reactions entails condensation of formaldehyde and dimethylamine. This reaction produces first the carbinolamine (a hemiaminal) and bis(dimethylamino)methane ():
Me2NH + CH2O -> Me2NCH2OH
Me2NH + Me2NCH2OH -> Me2NCH2NMe2 + H2O
The reaction of formaldehyde with carbazole, which is weakly basic, proceed similarly:
Again, this carbinol converts readily to the methylene-linked bis(carbazole).
Hemiaminal ethers have the following structure: R′′′-C(NR'2)(OR")-R′′′′. The glycosylamines are examples of cyclic hemiaminal ethers.
Methanolamine.svg|[[methanolamine]], an intermediate in the reaction of ammonia with formaldehyde
OC(NHCH2OH)2.
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In organic chemistry, an imine (ᵻˈmiːn or ˈɪmɪn) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bonds. Imines are common in synthetic and naturally occurring compounds and they participate in many reactions. For ketimines and aldimines, respectively, the five core atoms (C2C=NX and C(H)C=NX, X = H or C) are coplanar.
In organic chemistry, an aldehyde (ˈældᵻhaɪd) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are a common motif in many chemicals important in technology and biology. Aldehyde molecules have a central carbon atom that is connected by a double bond to oxygen, a single bond to hydrogen and another single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen.
Formaldehyde (fɔːrˈmældɪhaɪd , USalsofər- ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section Forms below), hence it is stored as an aqueous solution (formalin), which is also used to store animal specimens. It is the simplest of the aldehydes () and one of the simplest of the carbohydrates. The common name of this substance comes from its similarity and relation to formic acid.
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