Ueber die Einwirkung der Cyansäure auf Alkohol und auf Aldehyd

Liebig, J.; Wöhler, F.

doi:10.1002/jlac.18460590304

Cited by 10 publications

(6 citation statements)

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“…The most frequently used procedure for the preparation of allophanates is the reaction of an alcohol with cyanic acid. Cyanuric acid is depolymerized to cyanic acid in a stream of carbon dioxide or nitrogen and passed into the alcohol (23,84,95,129,130,165,194,210,219) or into a solution of the alcohol in an inert solvent (108,222). Alternatively, the cyanic acid may be condensed (b.p.…”

Section: A From Cyanic Acidmentioning

confidence: 99%

“…The hydrolysis of allophanates may be effected readily by warm alkalies (4,29,118,130,171,186). After purification and saponification, the pure alcohol and water-soluble products are obtained-an excellent way in which to purify an alcohol.…”

Section: Ohmentioning

confidence: 99%

“…Salts of allophanates have been prepared by the reaction of bases with ethyl allophanate (18,60,130,176,208). In this way, the barium (130,176), calcium (130), potassium (130,143), and sodium (60, 130) salts have been prepared.…”

Section: Ohmentioning

confidence: 99%

“…The sodium salt has also been prepared by double decomposition of the barium salt with sodium sulfate (130). The potassium salt has been obtained by adding ethyl allophanate to a solution of potassium amide in liquid ammonia (18).…”

Section: Ohmentioning

confidence: 99%

“…It was in 1830 that Liebig and Wohler (129) first reported the isolation of a new compound resulting from the treatment of methanol with cyanic acid. No physical constants nor analytical data were given by them until sixteen years later (130), when they set out the correct formula and analysis. Having been surprised in isolating neither a cyanide, a cyanate, nor a cyanurate, they named the compound an allophanate.4•6 Although this is the historical develop- ment as usually cited, the work of Richardson (166) and of Schlieper (186) must be considered.…”

Section: Introductionmentioning

confidence: 99%

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Allophanates.

Blohm¹,

Becker²

1952

Chem. Rev.

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concerning this article should be addressed to Ernest I. Becker at the Poly technic Institute of Brooklyn.4 Allophane: Greek allophanes, "appearing otherwise," from alios (otherwise) + phainesthai (to appear). 5 The term has also been used to describe a class of inorganic aluminum silicates. These are not under consideration here. Although «-and 7-substituted allophanates are also known, the discussion has been limited to esters of the unsubstituted acid:

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Section: A From Cyanic Acidmentioning

confidence: 99%

Section: Ohmentioning

confidence: 99%

Section: Ohmentioning

confidence: 99%

Section: Ohmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Allophanates.

Blohm¹,

Becker²

1952

Chem. Rev.

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[2+2]-Cycloreversionen

Schaumann

Ketcham

2006

Angewandte Chemie

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[2 + 2]‐Cycloreversions

Schaumann¹,

Ketcham²

1982

Angew. Chem. Int. Ed. Engl.

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Four-membered rings can be cleaved thermally, photochemically, or catalytically into two n: bonded fragments. Theoretical calculations, kinetic studies, and investigations of stereoand regioselectivity have been undertaken to clarify the question of whether the reaction involves one or two steps and to permit predictions on its course. [2 + 2]-Cycloreversions have been used to clarify the structure of four-membered rings, to prepare highly reactive n: electron-systems and-in combination with a [2 + 2]-cycloaddition-t0 protect double bonds.The combination of a cycloaddition and -reversion can be used to convert a carbonyl group into an olefin. Starting with compounds containing annelated four-membered rings, compounds with two functional groups or large ring systems can be prepared. (2 + 2]-Cycloreversions have also been discussed in connection with storage of solar energy. 3 5 We will classify a reaction as a [2+2]-cycloreversion only when two opposing o bonds of a carbo-or heterocyclic four-membered ring 3 are cleaved to give 112 or 4/5.Other terms used in the literature, "retrograde [2 + 21-cycloaddition", and "[4+2 + 2]-cycloelimination" are synonymous with [2 + 2]-cycloreversion. On the other hand, the concept "metathesis" has come to be used for the disproportionation of alkenes catalyzed by transition-metal compounds (cf. Section 4.1).If in 1-5, a/d and b/c are identical then the educts and products of the overall reaction of 112 to give 4/5 belong to the same chemical type, and only an exchange of substituents occurs. This specific type of cycloaddition and cycloreversion has been called an "exchange reaction" by Ul-The complete reaction often takes place in situ Angew. Chem. Inr. Ed. Engf. 21 (1982) 225-247 0 Verlag Chemie GrnbH, 6940 Weinheirn. 1982 0570-0833/82/0404-0225 S 02.50/0 Mechanism of 12 + 21-CycloreversionsAccording to the principle of microscopic reversibility the same considerations for the reaction mechanism must apply to the [2 + 2]-cycloreversion as to the [2 + 21-cycloaddition. If the two o-bonds are broken simultaneously, then according to the Woodward-Hoffmann rules['] for a thermally induced cleavage this corresponds to a [,2, + 02J process having transition state 11 in which the fragments separate from each other in a "corkscrew"[51 motion. A geometrically more favorable [,2, + ,2,]-reaction path via transition state l2[I4] is thermally "forbidden" i. e. would be associated with a much higher activation energy. In the case of photochemical [2 + 2]-cycloreversions the reverse relationships are expected, i. e. 12 would be favored over ll"].

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Ueber die Einwirkung der Cyansäure auf Alkohol und auf Aldehyd

Cited by 10 publications

References 0 publications

Allophanates.

Allophanates.

[2+2]-Cycloreversionen

[2 + 2]‐Cycloreversions

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