Sunday, April 07, 2013

What is the meaning of Alkenes? Concept, Definition of Alkenes

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Definition of alkenes


1 Meaning of alkenes

Olefins or Alkenes are unsaturated hydrocarbons which have one or more double bonds carbon-carbon bond in the molecule. He is that an alkene is nothing more than an alkane that has lost two atoms of hydrogen producing as a result a double bond between two carbons. Cyclic Alkenes are called cycloalkene.
The general formula of an open with only double link chain alkene is CnH2n. For each additional double bond there will be two hydrogen atoms less than those indicated in this formula.
As it happens with other organic compounds, some Alkenes are known by their non-systematic names, in which case the completion routine by - filled-eno, is replaced as it is the case of the ethene that sometimes is called ethylene, propene by propylene or.

Systematic nomenclature (IUPAC)

1 Appoint the main hydrocarbon: has to be find longest carbonated chain containing the double bond, not necessarily that of larger, placing locators that have the fewest links double, double-numbering of the carbon atoms in the chain starting at the end closest to the link. Note: If a list from left to right and from right to left, the 134.7 locators are equal, seeks that the double bonds have lower locator or lower position.
2. If the main chain has the same substituents on the same carbon atom separating comma numbers locators that are repeated in the atom, these are separated by a dash of prefixes: Di, Tri, Tetra, etc. Respectively to the number of times to repeat the substituent.
3. The substituents are written according to the alphabetical order with their respective Locator.
4. If in the main chain, there are several substituents branched equals is placed number locator in the chain leading to separated by a hyphen, and writes the prefix corresponding to the number of times to repeat with prefixes: Bis, Tris, Tetrakis, Pentaquis, etc. Followed by a parenthesis within which refers to the complex substituent with termination - IL
5 Made all the above with respect to substituents, is placed the number of Locator of the double link in the main chain separated from a hyphen, followed by the name according to the number of carbon atoms by replacing the Ano completion by the suffix - eno.
6. If you have more than one double bond, it is named indicating the position of each of the double bonds with their respective number Locator, is written to the root of the name of the alkene from which it comes, followed by a number prefix: di, tri, tetra, etc. and using the suffix - eno. Ex: - Diene, - trieno and so on.
Nomenclatura alquenos.JPG


2. Definition of alkenes

Alkenes or unsaturated compounds, also called olefins or hydrocarbons etilenicos, are those colorless hydrocarbons, in which its molecules contain the double bond carbon-carbon, and this is what determines their properties. The simplest alkene is ethene, their nuclei are at the same level, so it is a co-planar molecule. Its h-c - H bond angles are approximately 121 th and the link h-c - H of 118 degrees.
The difference with alkanes, is the loss of two hydrogen atoms. Alkenes have greater reactivity than the alkanes and more acidity.
The suffix "year" used in the alkanes by "eno" must be changed according to the IUPAC for naming alkenes, indicating with a number, where resides the double link. The number of the double bond is the first carbon that sustains it, putting that number to the main name of the hydrocarbon.
Alkenes, in the first three terms of the series are gases, then to number 18, are solid, and the following, are liquid. They are soluble in organic solvents, but not in water.
Hydrogenation (exothermic reaction between alkenes and hydrogen) is used to determine their relative stabilities.
In a same hydrocarbon there may be two or more links, what gets the polyenes or Polyfunctional alkenes. If the double bonds follows a molecule, cumulative double bonds are called.
There are four General methods which are based on elimination reactions for the preparation of alkenes: the dehydrogenation of alkanes, alcohols dehydration, the deshidrohalogenacion of halides of alkyl and the tarnishing of vic-dihaluros.

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