Presentation on theme: "Properties and Reactions of Hydrocarbons. Properties of Hydrocarbons Made up of mostly C and H Relatively nonpolar Low solubility in polar solvents."— Presentation transcript:
Properties of Hydrocarbons Made up of mostly C and H Relatively nonpolar Low solubility in polar solvents (e.g. water) Good solvents for other nonpolar molecules Mostly london-dispersion forces (weak) Low boiling and melting points
Reactivity of Hydrocarbons Alkanes are generally less reactive than alkenes or alkynes Aromatic compounds are more reactive than alkanes, but less reactive than alkenes and alkynes. Alkanes < aromatics < alkenes < alkynes
Reactions of Alkanes Single bonds between carbon atoms are difficult to break. (This is why alkanes are relatively unreactive) Can undergo combustion reactions
Reactions of Hydrocarbons Combustion: Hydrocarbons burn readily in air to produce carbon dioxide and water. Incomplete Combustion: Produces carbon and poisonous carbon monoxide. C 3 H 8(g) + 5 O 2(g) --> 3CO 2(g) + H 2 O (g) C 3 H 8(g) + 7/2 O 2(g) --> C (s) + CO (g) CO 2(g) + 4 H 2 O (g)
Reactions of Alkanes Substitution Reactions: Hydrogen atoms may be substituted by a halogen. The product is a halogenated alkane (alkyl halides)
Reactions of Alkenes and Alkynes Addition Reactions: Reactions in which a molecule is added to a double or triple bond (by breaking it). No loss of hydrogen atoms from the hydrocarbon
Markovnikov’s Rule When molecules with two identical atoms (e.g. H 2 ) are added to a double bond, only one possible product is formed. When molecules of nonidentical atoms (e.g. HBr) are added, two different products are theoretically possible
Markovnikov’s Rule However, experiments show that only one main product is formed. This product can be predicted by Markovnikov’s rule “The rich get richer” When a hydrogen halide is added to an alkene or alkyne, the hydrogen atom bonds to the carbon atom that already has more hydrogen atoms.
Benzene Does not act as 3 single bonds and 3 double bonds It’s 6 identical bonds of intermediate length Due to hybridization (delocalized, shared electrons)
Reactions of Aromatic Hydrocarbons (Benzene) Less reactive than alkenes and do not undergo addition reactions unless under conditions of extreme temperature or pressure Do undergo substitution reactions (more reactive than alkanes)
Organic Halides Properties Halogen makes the molecule more polar, increasing strength of the intermolecular forces –Higher boiling points than their corresponding hydrocarbons –More soluble in polar solvents Molecules with more halogens are more polar
Preparing Organic Halides Recall: Substitution reaction produce halides in alkanes and aromatic hydrocarbons
Preparing Organic Halides Recall: alkyl halides are produced in halogenation reactions (addition) with alkenes/alkynes
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