Organic Chemistry (Alkanes) Organic: Any chemical compound that contains carbon, with the exception of oxides (CO 2 ), carbonates (CO 3 2- ), and carbides (SiC). Catenation: The covalent bonding of an element to itself in order to form chains or rings. (Carbon) Hydrocarbons: Compounds that only contain carbon and hydrogen atoms. Saturated: A hydrocarbon containing the maximum number of hydrogens possible. (All single bonds)

Homologous series: A group of compounds that has a constant increment of change.

Properties Low mass alkanes (C  C 4 ) – Gaseous (Natural gas) – Low boiling points Medium mass alkanes (C 5  C 16 ) – Liquids High mass alkanes(C 17  ) – Solids – High boiling points Alkanes are generally stable due to the high bond enthalpies (strong bonds) and low polarities. They are also generally very combustible. Larger masses have more van der Waal forces. Spherical will have less.

Fractional Distillation of crude oil is based on this concept.

Alkane: A hydrocarbon in which there are only single covalent bonds. – The carbons are arranged in chains, branches, or rings. – The molecules are non-polar – Series formula = C n H 2n+2

4 Ways to write a formula in Organic Chem. Butane C 4 H 10 H H C-C-C-C H H HH CH 3 -CH 2 -CH 2 -CH 3 Molecular formula Structural formula Condensed structural formula Line-angle formula

Parent alkane: The longest continuous carbon chain with the most branches. Substituent: Anything that takes the place of hydrogen. – Ex) Halogens, O, N, S, P – Alkyl Group: A hydrocarbon substituent. Add –yl to the group’s name. CH 3 -CH-CH 2 -CH 3 CH 3

Unsaturated Hydrocarbons Unsaturated: Hydrocarbons in which not all carbon atoms have four single covalent bonds. Alkene: Alkynes:

Physical properties similar to alkanes. – Nonpolar or low polarity – B.P. increases as molar mass increases. (Volatility decreases) – Insoluble in water – Combust the same The double bond makes them more reactive Test for unsaturation – Add a few drops of bromine water and shake. Should go from orange/yellow to clear.

Importance of alkenes Addition reactions – Margarine: Hydrogenation of polyunsaturated lipids. Use nickel catalyst and pressure Some double bonds are broken. – Pack more closely increasing van der waals’ which causes them to solidify (High MP) – Ethanol: Solvent, fuel, intermediate for esters, drinks Industry: Hydrate ethene. – Plastics

Naming Rules 1.Count the longest parent alkane, alkene or alkyne.  Longest chain with the double or triple bond.  End the name in: Alkane: -ane Alkene : -ene Alkyne: -yne 2.Want bonds to have lowest numbers  If there is more than one bond, the suffix is modified to describe how many. (2 = adiene, 3 = atriene) 3.Substituents in alpha order. Lowest numbers possible. 4.Separate numbers with commas, number and name with a hyphen. 5.Ring structures get the prefix “cyclo”

Benzene (C 6 H 6 ) Called an aromatic hydrocarbon. – Usually in stuff that smells. If only one small group (Cl, NO 2, CH 3 ) is attached, naming rules are the same as alkanes except you will use benzene for the parent chain. If benzene is a substituent of a long chain, it is called “phenyl”. Has delocalized electrons.

Benzene switches “resonates” between two different structures.

Homework Chapter 22 #18a b, 21 a d, 22c, 26, 28, 32e g What are the trends observed in a homologous series? Explain why these trends are observed. Match each boiling point (9.5 o C, 27.9 o C, 36.3 o C) with the appropriate compound. Explain each. – 2-methylbutane, pentane, 2,2-dimethylpropane