ORGANIC CHEMISTRY! Introduction CHAPTER

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L EARNING G OALS Understand and identify the difference between hydrocarbons - alkanes, alkenes & alkynes. Understand how to name & draw hydrocarbons using IUPAC naming system. Identify and predict chemical reactions involving hydrocarbons.

W HAT ARE H YDROCARBONS ? Hydrocarbons – Organic molecules composed (made) of Carbon and Hydrogen atoms only.

F UNCTIONAL G ROUPS

W AYS TO R EPRESENT O RGANIC C OMPOUNDS Type of formulaExample Molecular formula C 4 H 10 O Structural formula Skeletal formula Condensed structural formula

A LKANES, A LKENES, A LKYNES Alkanes – A saturated hydrocarbon containing only single bonds. Alkenes – An unsaturated hydrocarbon containing at least 1 double bond. Alkynes – An unsaturated hydrocarbon containing at least 1 triple bond.

N OMENCLATURE (N AMING ) OF A LKANES Alkanes are named with the suffix -ane The prefix indicates the longest straight chain in the molecule. Alkyl branches are named with the prefix for the branch followed by the suffix -yl. Numerals are separated by commas, numerals and letters by hyphens, and names of branches and parent chains are NOT separated.

N OMENCLATURE (N AMING ) OF A LKANES Step 1: Identify the longest carbon chain (it may travel through branches). Step 2: Number the carbon atoms, starting with the end closest to the branch(es). Step 3: Name each branch and identify its location on the parent chain, (the name with the lowest numerals is preferred.) Step 4: Write the IUPAC name: number of location – branch name parent name. Step 5: List branches in alphabetical order. * Note : The presence and location of multiple alkyl branches is indicated by the prefixes di-, tri-, etc. (e.g. 2,2,3-trimethylbutane). Example:

E XAMPLE : N AMING A LKANES 1. Write the IUPAC name for the following alkane: 2. Draw the structural formula for 4,6-dimethyl-5-propyldecane: 3,4,4-trimethylheptane

P ROPYL & B UTYL (A LKYL ) G ROUPS Recall: Isomers have the same Molecular Formula, but different Structural Formula

N AMING A LKENES AND A LKYNES Use the same rules for alkanes, except with the suffixes -ene (for alkenes), and -yne (for alkynes). When numbering carbon atoms in the parent chain, begin with the end closest to the multiple bond. Insert hyphens (-) between the branch chain and the parent chain to show where the carbon double or triple bond is located. (e.g. 3-methyl-1-butene) The presence and location of multiple double or triple bonds is indicated by the prefixes di-, tri-, etc. (e.g. 2,4,6-octa tri ene).

E XAMPLE : N AMING A LKENES Draw the Structural formula for 1,3,5-hexatriene : Write the IUPAC name for the following structure: 3-ethyl-2-hexene OR 3-ethylhex-2-ene

E XAMPLE : N AMING A LKYNES Write the IUPAC name for the following structural diagram: 5-ethyl-4-methylhept-2-yne OR 5-ethyl-4-methyl--2-heptyne

C YCLIC H YDROCARBONS For cyclic hydrocarbons, the carbons that form the ring are the parent chain. The prefix cyclo- is added. Example: What is the IUPAC name for the following structure? 3,5-dimethylcyclohexene

A ROMATIC H YDROCARBONS (BENZENE) Benzene – An aromatic 6 carbon cyclic molecule which contains alternating double bonds.

N AMING A ROMATIC COMPOUNDS (B ENZENE ) If an alkyl group is attached to a benzene ring, the compound is named as an alkylbenzene. Example: Methylbenzene Alternatively, the benzene ring may be considered as a branch of a large molecule; in this case, the benzene ring is called a phenyl group

N AMING A ROMATIC COMPOUNDS (B ENZENE ) If more than one alkyl group is attached to a benzene ring, the groups are numbered using the lowest numbers possible, starting with one of the added groups. Example: ortho meta para

P ROPERTIES OF HYDROCARBONS All hydrocarbons have relatively non-polar bonds. Only weak forces like van der Waals (London) forces (the attraction of one molecule's nuclei to another's electrons) hold them together. This gives them low melting and boiling points, and they are not water soluble (non-polar). Benzene is very stable because of its delocalization of electron. Therefore, it has a higher melting and boiling point.

R EACTIONS INVOLVING ALKANES COMBUSTION (burning) C 3 H 8 (g) 5 O 2 (g) → 3 CO 2 (g) 4 H 2 O(g) Hydrocarbon + oxygen gas  carbon dioxide + water

R EACTIONS INVOLVING ALKANES SUBSTITUTION Alkyl Halide

R EACTIONS INVOLVING ALKENES & ALKYNES HALOGENTION (Addition) Halogens add to a double or triple bond. (e.g. Br 2 or Cl 2 )

R EACTIONS INVOLVING ALKENES & ALKYNES HYDROGENATION (Addition) Hydrogen adds to the double or triple bond. (H 2 )

R EACTIONS INVOLVING ALKENES & ALKYNES HYDROHALOGENTION (Addition) A hydrogen halide adds atoms to the double or triple bond. (e.g. HBr) Markovnikov’s Rule...

M ARKOVNIKOV ’ S R ULE ! When molecules of non-identical atoms are added, two different products are theoretically possible. Markovnivov’s Rule: When a hydrogen halide or water is added to an alkene or alkyne, the hydrogen atom bonds to the carbon atom within the double bond that already has more hydrogen atoms. This rule may be remembered simply as “the rich get richer.”

R EACTIONS INVOLVING ALKENES & ALKYNES HYDRATION (Addition) Water (H 2 O) adds to the double or triple bond, placing a hydrogen (H) on one carbon and a hydroxyl group (OH) on the other....Don’t forget Markovnikov’s Rule!

R EACTIONS WITH AROMATIC HYDROCARBONS Aromatic hydrocarbons are less reactive than alkenes and alkynes, and the benzene ring will only undergo addition reactions under extreme temperature and pressure. However, it is easy to replace hydrogen atoms in the ring by substitution reactions...

R EACTIONS WITH AROMATIC HYDROCARBONS SUBSTITUTION These reactions will not occur without catalyst

H OMEWORK / PRACTICE PROBLEMS