Ring expansion reaction
Encyclopedia
In chemistry, ring expansion and ring contraction are chemical reactions that increase or decrease, respectively, the number of atoms in a ring of a cyclic compound
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Cyclic compound
In chemistry, a cyclic compound is a compound in which a series of atoms is connected to form a loop or ring.While the vast majority of cyclic compounds are organic, a few inorganic substances form cyclic compounds as well, including sulfur, silanes, phosphanes, phosphoric acid, and triboric acid. ...
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Ring expansion reactions
Examples of ring expansion reactions are:- the Beckmann rearrangementBeckmann rearrangementThe Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann , is an acid-catalyzed rearrangement of an oxime to an amide...
- the Dowd-Beckwith ring expansion reactionDowd-Beckwith ring expansion reactionThe Dowd–Beckwith ring expansion reaction is an organic reaction in which a cyclic β-keto ester is expanded by up to 4 carbons in a free radical ring expansion reaction through an α-alkylhalo substituent . The radical initiator system is based on AIBN and tributyltin hydride. The cyclic β-keto...
. - the Tiffeneau-Demjanov rearrangementTiffeneau-Demjanov rearrangementThe Tiffeneau-Demjanov rearrangement is the chemical reaction of a 1-aminomethyl-cycloalkanol with nitrous acid to form an enlarged cycloketone....
- the vinylcyclopropane-cyclopentene rearrangement
Ring contraction reactions
Examples of ring contraction reactions are:- the Favorskii rearrangementFavorskii rearrangementThe Favorskii rearrangement , named for the Russian chemist Alexei Yevgrafovich Favorskii, is most principally a rearrangement of cyclopropanones and α-halo ketones which leads to carboxylic acid derivatives. In the case of cyclic α-halo ketones, the Favorski rearrangement constitutes a ring...
- the Demjanov rearrangementDemjanov rearrangementThe Demjanov rearrangement is the chemical reaction of primary amines with nitrous acid to give rearranged alcohols. It involves substitution by a hydroxyl group with a possible ring expansion. It is named after the Russian chemist Nikolai Jakovlevich Demjanov...
- Ring contractions of cyclic ketoneKetoneIn organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
s and cycloalkeneCycloalkeneA cycloalkene or cycloolefin is a type of alkene hydrocarbon which contains a closed ring of carbon atoms, but has no aromatic character. Some cycloalkenes, such as cyclobutene and cyclopentene, can be used as monomers to produce polymer chains. Unless the rings are very large, cycloalkenes are...
s brought about by hypervalent iodine for example the reaction of cyclohexeneCyclohexeneCyclohexene is a hydrocarbon with the formula C6H10. This cycloalkene is a colorless liquid with a sharp smell. It is an intermediate in various industrial processes...
with iodosobenzeneIodosobenzeneIodosobenzene or iodosylbenzene is an organoiodine compound with the empirical formula C6H5IO. This colourless solid compound is used as an oxo transfer reagent in research laboratories examining organic and coordination chemistry...
and boron trifluorideBoron trifluorideBoron trifluoride is the chemical compound with the formula BF3. This pungent colourless toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds.-Structure and bonding:...
to cyclopentanecarbaldehyde: