From Halogenated Carbonates

Cyclic carbonates have been obtained in 82-90% yield by heating monohalogen-ated linear organic carbonates at 353-373 K for l-4h (Equation 7.19) [199]. This process involved an internal nucleophilic attack of the carbonate onto the alicyclic 

Similar results have been obtained starting from di-halogenated carbonates 

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Dehydrohalogenation (Section 5 14) Reaction in which an alkyl halide on being treated with a base such as sodium ethoxide is converted to an alkene by loss of a proton from one carbon and the halogen from the adjacent carbon... 

The leaving group doesn t have to be a water molecule any group or substituent which upon cleavage from the carbon skeleton under appropriate reaction conditions leaves behind a carbenium ion—e.g. a halogen substituent—will suffice. The other substituents can be hydrogen, alkyl or aryl. ... 

Another route commonly used in the laboratory to produce alkenes is the dehydrohalogenation of haloalkanes, the removal of a hydrogen atom and a halogen atom from neighboring carbon atoms ... 

Marvel, Sample, and Roy concluded that cyclopropane rings were formed when a dilute solution of poly-(vinyl chloride) in dioxane was treated with zinc, which removes halogen atoms from alternate carbon atoms. Only 84 to 86 percent of the chlorine could be removed, however, a result which was attributed to the occasional isolation of a lone substituent between reacted neighbors. The structure of the product was presumed to be... 

Organometallic compounds or carbanions undergo a number of reactions in which the carbanion or carbanion-like moiety of the organometallic compound acts as a nucleophilic displacing agent. Examples are the formation of hydrocarbons from alkyl halides, alkyl halides from halogens, and ketones from acid chlorides or esters. The latter two reactions are closely related to the base-catalyzed condensations and are perhaps additions as well as displacement reactions. Related addition reactions are the carbonation of organometallic compounds and the addition to ketones or aldehydes. 

When a haloalkane with p-hydrogen atom Is heated with alcoholic solution of potassium hydroxide, there Is elimination of hydrogen atom from p-carbon and a halogen atom from the a-carbon atom. As a result, an alkene is formed as a product. Since p-hydrogen atom is involved in elimination. It Is often called p-elimination. 

Apart from the carbon-halogen bond, the carbon-oxygen one is rather active toward the reductive cleavage due to its polarity, so different types of compounds bearing a carbon-oxygen bond are able to undergo this reaction. 

The stability of dialkylimidazolium cation-containing ionic liquids can be a problem even at moderate temperatures in the presence of some reagents or catalysts. For example, when CsF and KF were used in the ionic liquid [BMIM]PFg to perform a halogen exchange reaction in an attempt to replace Br from bromo-carbons with F , it was found that alkyl elimination from the [BMIM] cation took place, forming methyl imidazole, 1-butene, 1-fluorobutane, and other unidentified products at 150°C overnight 69). The fluoride ion acted as a base that promotes elimination or substitution processes. 

In a /3-elimination (dehydrohalogenation) reaction a halogen and a hydrogen atom are removed from adjacent carbon atoms to form a double bond between the two C s. The reagent commonly used to remove HX is the strong base KOH in ethanol (cf. Section 6.2). 

Allenes are generally prepared by elimination of halogens, hydrogen halides, or water from adjacent carbon atoms, the dehalogenation of gem-dihalocyclo-propanes, rearrangement of acetylenes, and the 1,4-addition to vinylacetylenes. 

B., 2, 720 28, R., 466.)—The use of metals—sodium, copper, silver—to eliminate halogen from halogen compounds, and bring about the condensation of the carbons to which the halogen atoms are attached has, as... 

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