Ciencias de la tierra II Alkenes (Session 31) Ciencias de la tierra II

Ciencias de la tierra II Alkenes Known under the name of olefinic hydrocarbons, they are characterized by being formed by carbon and hydrogen linked by simple covalent bonds and they present one or more double covalent bonds carbon-carbon. General Formula CnH 2n Ciencias de la tierra II

Ciencias de la tierra II Nomenclature The basic IUPAC rules are applied. The ending (suffix) for Alkenes is “ene”. The longest C chain that has double bonds is picked to give the base name of the alkene. The longest carbon chain is numbered by the extreme that is closest to the double bond. Ciencias de la tierra II

Ciencias de la tierra II Nomenclature We place prior to the name the lowest carbon number that forms the double bond to indicate its position in the chain. For example 3 octane. If it is branched we add prior to the base name the positions and names of the branches. Ciencias de la tierra II

Isomeric cis and trans. Isomers Configurations Alkenes can present isomeric configurations due to the presence of the double bond. The configurationally isomers differ in the distribution of atoms in the space. Example two 2,3-dichloroide-2-butane CH3 CH3 Cl CH3 C = C C = C Cl Cl Cl CH3 Ciencias de la tierra II 2,3-dichloride-cis-2-butane 2,3-dichloride-trans-2-butane

Ciencias de la tierra II Physical Properties The first the 3 Alkenes are gases at room temperature, the ones that have from 5 to 18 C atoms are liquids and the ones of 18 or more C atoms are solids. The boiling points increase when the molecular weight of the alkene increases, linear alkenes have higher boiling points then the branched ones with similar molecular weight. Alkenes are insoluble in water but are soluble in in non polar solvents like ethers, hexane, tetrachloride of carbon, etc. Alkenes are less dense in water, for this reason they float in it. Ciencias de la tierra II

Ciencias de la tierra II Chemical Properties Addition of hydrogen (Catalytic hydrogenation). Addition of sulfuric acid and water (Markovnikov Law). Addition of hydrogen halides (HX) Oxidation Ciencias de la tierra II

Applications and importance of Alkenes Sources of energy (gases) Solvents (hexane) Primary material for the formation of a large quantity of polymers and plastics (ethylene and propylene). Hormones for the maturing of vegetables (ethylene) Ciencias de la tierra II

Ciencias de la tierra II Bibliography Bloomfield, M. (1997) Chemistry in Living Organisms. 1st ed. Mexico: LIMUSA Devore, G. et al.. (1969). Organic Chemistry. 1st ed. Mexico: Cultural Publications Rakoff, H. et al. (1992) Fundamental Organic Chemistry. 1st ed. Mexico: LIMUSA Solomons, G. (1996) Fundaments of Organic Chemistry. 2nd. ed. Mexico: LIMUSA Ciencias de la tierra II