Organic Chemistry • Chemical compounds fall into one of two categories: • Organic compounds • Inorganic compounds • Organic compounds can be found naturally or they can be synthesized, but they all contain C and a few other elements. • There are far more organic compounds than inorganic compounds.
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Properties of Organic Compounds • usually molecular (contain non-metals bonded with covalent bonds) • low melting points • nonpolar (insoluble, or only slightly soluble, in water) • very stable (not reactive)
Carbon • Carbon forms 4 covalent bonds, i.e., it will share electrons with 4 other elements. • Prefixes are used in the name to indicate how many carbons are in the compound.
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Alkanes • Alkanes are hydrocarbons (consisting of only C and H) that only contain single bonds. • Start with the Prefix that matches the number of carbons • Alkanes have the ending –ane in their name.
HI – C– H H IH CH4 • Draw the structural formula One carbon is meth + “ane” ending So this is Methane
HI HI – C–C– H H IH IH C2H6 • Draw the structural formula Two carbons is eth + “ane” ending So this is Ethane May also be drawn as CH3-CH3
C3H8 Structural formula: Three carbons is prop + “ane” ending So this is Propane HI HI HI – C–C–C– H H IH IH IH May also be drawn as CH3-CH2-CH3
C4H10 • There are two possible structural formulas: HI HI HI HI This is n-butane because it is a straight chain – C–C–C–C– H H IH IH IH IH May also be drawn as CH3-CH2-CH2-CH3
HIC| -H H- HI HI – C–C–C– H H IH IH IH OR This is 2-methyl propane because there is a methyl side group off of the 2nd carbon in the propane chain.
Isomers • are compounds that have the same molecular formula, but different structural formulas. • Isomers usually have different chemical and physical properties as well. • We must have some way of specifying which form of butane we are talking about.
Normal Alkanes • Alkanes that have a continuous chain of carbons are called normal alkanes. • The first isomer of butane is a normal alkane and is sometimes referred to as n-butane.
Branched Alkanes • The second isomer has a branch off the second carbon. • These branches are referred to as alkyl groups. • The name of the alkyl group is determined by the prefix according to the number of carbons and the ending “-yl” • The branch in this case would be called methyl
Rules for Naming Alkanes • Count the carbons of the longest continuous chain. This will be the prefix. Add –ane to it. • Name the alkyl groups attached to the main chain. If there are two or more of the same name, use the counting prefixes (di, tri, etc.)
Rules for Naming Alkanes, cont’d • Number the carbons, starting with the carbon closest to the branch. • List the alkyl groups first, in alphabetical order, using a number to indicate which carbon it branches from.
HIC| -H H- HI HI – C–C–C– H H IH IH IH This would be called 2-methyl propane
CH3| CH3–CH–CH3 This is a short-hand way of writing the same formula: