Hemi-

Acid-catalyzed formation of a hemiacetal (hemiacetal) from an aldehyde (left) and an alcohol (middle). R ¹ and R ² are organyl radicals, for example alkyl or aryl radicals, R ¹ can also be a hydrogen atom.

Hemi (Greek), also semi (Latin), means half.

Organic chemistry

Hemiaminal

Hemiacetals are sometimes hemiacetals called and are derived from aldehydes. The acid-catalyzed reaction of ketones with alcohols results in hemiketals in the first step . Hemiaminals are also derived from aldehydes or ketones through reaction with ammonia, primary or secondary amines. Hemiterpenes are organic-chemical compounds made up of five carbon atoms and based on the isoprene structure.

The term hemicellulose is based on the original, incorrect assumption that it is a precursor of cellulose . However, hemicellulose is a homopolymer of glucose .

Inorganic chemistry

Hemihydrates (hemihydrates) is a name for compounds whose crystallization only contains half a mole of water per mole in the crystal. Furthermore, “hemihydrate” is a name for two modifications of a gypsum with the composition CaSO ₄ · 0.5 H ₂ O.

Individual evidence

1. ^ Philipp Fresenius and Klaus Görlitzer: Organic-chemical nomenclature , 3rd edition, Wissenschaftliche Verlagsgesellschaft, Stuttgart 1991, ISBN 3-8047-1167-7 , p. 216.
2. ↑ Jerry March: Advanced Organic Chemistry , 3rd Edition, John Wiley & Sons, New York 1985, ISBN 0-471-88841-9 , pp. 796-797.
3. ↑ ^{a b} Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 3: H-L. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1983, ISBN 3-440-04513-7 , p. 1671.