IR SPECTRUM OF ALKENES Besides the presence of C-H bonds, alkenes also show sharp, medium bands corresponding to the C=C bond stretching vibration at about 1600-1700 cm-1. The melting point of alkenes is similar to that of alkanes. Alkenes have a functional group C=C – the part of the molecule that takes part in reactions. Alkanes, in contrast, do not have a functional group and are less reactive as a result. The shape of an organic molecule is influenced by the presence of this bond, and the double bond is the site of most of the chemical reactions that alkenes undergo. Visit http://www.chemistry.jamesmungall.co.uk for notes on this topic. Triple-bonded carbons are sp-hybridized, and have linear shapes, with the bonded atoms at angles of 180° to each other. The ammonium ion, NH 4 + The nitrogen has 5 outer electrons, plus another 4 from the four hydrogens - making … Water is described as bent or V-shaped. Alkenes are weakly polar just like alkanes but are slightly more reactive than alkanes due to the presence of double bonds. Like other hydrocarbons, the alkenes are insoluble in water but soluble in organic solvents. An alkene is a compound that belongs to the family of hydrocarbons. Alkenes, also referred to as olefins, are organic unsaturated hydrocarbons that are made of carbon and hydrogen atoms with one or more carbon-carbon double bonds in their chemical structure. Alkenes are weakly polar just like alkanes but are slightly more reactive than alkanes due to the presence of double bonds. Here are some basic rules for naming alkenes from the International Union of Pure and Applied Chemistry (IUPAC): The longest chain of carbon atoms containing the double bond is considered the parent chain. Alkynes, containing a carbon-carbon triple bond, have the linear or straight geometry as a primary feature. For molecules with the same number of carbon atoms and the same general shape, the boiling points usually differ only slightly, just as we would expect for substances whose molar mass differs by only 2 u (equivalent to two hydrogen atoms). However, cis-isomer molecules have a lower melting point than trans- isomers as the molecules are packed in a U-bending shape. Additionally, alkenes are also identified as unsaturated hydrocarbons, as they have less than the maximum number of hydrogen atoms per carbon atoms. The shape isn't described as tetrahedral, because we only "see" the oxygen and the hydrogens - not the lone pairs. Thus the compound CH 2 =CHCH 3 is propene. Moreover, it has a carbon-carbon double bond (C=C). However, cis-isomer molecules have a lower melting point than trans- isomers as the molecules are packed in a U-bending shape. 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