Carbon: More Than Just Another Element Chapter 10

10.1 Why Carbon? Organic compounds contain the element carbon, which can bond with other carbon atoms to form straight chains and branched chains. Isomers –identical composition but linked in different ways

10.2 Hydrocarbons Carbon and hydrogen only! Alkanes, cycloalkanes AlkenesAlkynes Aromatic compounds

Alkanes Alkanes contain only single bonds between carbon atoms. Alkanes and other organic compounds are best represented by structural formulas and can be named using systematic rules determined by the International Union of Pure and Applied Chemistry (IUPAC).

Alkanes Each alkane has the general formula C n H 2n+2 ; n is the number of carbon atoms. Straight-chain hydrocarbons, also called unbranched or normal, all carbon atoms are connected in a long chain. The name of each alkane ends in the suffix “-ane”.

Alkanes The root of the name corresponds to the longest carbon chain in the compound Substituent groups are identified by a name and position in the carbon chain –called alkyl group 2 or more of the same alkyl group (use di-,tri-,tetra-) otherwise list in alphabetical

NameFormulaNameFormula Methane CH 4 Hexane C 6 H 14 Ethane C2H6C2H6C2H6C2H6Heptane C 7 H 16 Propane C3H8C3H8C3H8C3H8Octane C 8 H 18 Butane C 4 H 10 Nonane C 9 H 20 Pentane C 5 H 12 Decane C 10 H 22

Saturated Compounds Saturated hydrocarbons have all carbon-carbon single bonds. Unsaturated hydrocarbons contain carbon-carbon multiple bonds.

Cyclic Alkanes and Alkane Properties Alkanes that contain hydrocarbon rings are called cyclic alkanes. Alkanes are nonpolar compounds that have low reactivity and lower melting points and boiling points than polar molecules of similar size and mass.

Alkenes and Alkynes Alkenes and alkynes are hydrocarbons that contain at least one double or triple bond, respectively. Alkenes and alkynes are nonpolar compounds with greater reactivity than alkanes but with other properties similar to alkanes.

Alkenes and Alkynes Alkenes and alkynes can also be named using IUPAC rules. Look at the longest chain to figure out the “parent name”. Alkenes have the general formula of C n H 2n. –Root ending is “-ene” Alkynes have the general formula of C n H 2n-2. –Root ending is “-yne”

Naming Isomers Look at the longest continuous chain that determines the root name. This is the last part of the name. Next name the alkyl group that substitutes on the parent chain. Specify the location of the groups by numbering longest chain sequentially. –hexane vs. 2-methylpentane vs. 2,3 – –hexane vs. 2-methylpentane vs. 2,3 – dimethylbutane vs. 2,2 - dimethylbutane

Naming Isomers Alkenes exhibit cis-trans isomerism because rotation around the double bond is restricted. –In cis isomerism the heavier groups are on the same side of the double bond. –In trans isomerism the heavier groups are on opposite sides of the double bond.

cis – 2-pentene trans-2-pentene

Aromatic Hydrocarbons and Petroleum Aromatic hydrocarbons contain benzene rings as part of their molecular structures. Nonaromatic hydrocarbons are called aliphatic hydrocarbons. –tend to be less reactive than alkenes or alkynes because they lack double bonds (electrons are evenly shared)

Aromatic Hydrocarbons May contain two or more benzene rings fused together Some are carcinogenic Major sources are petroleum and natural gas Fractional distillation can separate petroleum into components

10.3 Functional Groups HalideAlcoholEtherAldehydeKetone Carboxylic acid EsterAmideamine