CHEM 106 1nd Edition Lecture 5Outline of Last Lecture I. Functional groupsOutline of Current Lecture II. Monomers and PolymersIII. AlkanesIV. Drawing organic moleculesV. Structural isomersVI. Counting and Identifying IsomersVII. Naming AlkanesCurrent LectureChapter 13: Organic Chemistry (continued)Monomers and Polymers:Monomers combine to make polymers and polymers are commonly very large moleculesIndustrial (as opposed to biological) polymers are typically a mixture with somewhat different sizesIndustrial polymers can be designed to have specific properties (structure, density, strength, hardness, insulating)More details: 13.2 AlkanesHydrocarbons (CxHx) with only C-H bondsSaturated hydrocarbons: alkanes, maximum H/C ratioUnsaturated hydrocarbons: contain at least one >C=C< or -C≡C- groupUnsaturated hydrocarbons are converted to saturated hydrocarbons by hydrogenationPhysical properties of AlkanesStructure: Melting point: -190°CBoiling point: -42°CMelting point: -57°C H3C-(CH2)6-CH3 (octane)Boiling point: +126°CMelting point: +37°C H3C-(CH2)18-CH3 Boiling Point: +343°CDrawing Organic MoleculesAbbreviated versions of Lewis structuresLewis: bond angles may or may not be realistic (think in 3D) Condensed structure (no bonds)CH3CH2CH2CH3CH3(CH2)2CH3Skeleton structure – leave off H and C at ends and corners-CH3 methyl group makes 1 bond-CH2- methylene group makes 2 bondsStructural IsomersSame molecular formula, but different structure (+ properties)Ex: C4H10 Melting point: -138°CBoiling point: 0°CMelting point: -160°CBoiling point: -12°CLarger surface in contact, stronger dispersion forces (10.3)Structural variation involves branchingLarge molecules have many isomersCounting and Identifying IsomersIsomers must have the same molecular formula (check)Different orientations or conformations are not different isomersIsomers can only be interconverted by breaking + rearranging bondsEx: Structures that are identical= = Naming AlkanesPrefix for chain length (number of C’s)Prefix Structure AlkaneMeth CH4methaneEth CH3CH3ethaneProp CH3CH2CH3propaneBut CH3(CH2)2CH3butanePent CH3(CH2)3CH3pentaneHex CH3(CH2)4CH3hexaneHept CH3(CH2)5CH3heptaneOct CH3(CH2)6CH3octaneNon CH3(CH2)7CH3nonaneDec CH3(CH2)8CH3decaneNomenclatureSimple unbranched chain n- aneEx: n-heptane normal heptaneBranched chains:1. Select the longest unbranched chain2. Identify branches name by number of carbons with prefix + “ yl”Ex: -CH3methyl -CH2CH3ethyl3. Indicate the point of attachment of the branch to the main chain by carbon number (smallest)4. Multiple, identical groups attached to the same or different C are indicated by di, tri, tetra5. Multiple substituents are named alphabeticallyEx: name the following alkanesLongest chain: 8 c – octaneBranch: 2 c – ethylPosition 4 or 5, thus 4 (smaller)*4 ethyl octane (isomer of n-decane) Longest chain: 9 nonaneBranches: methyl 2, thus dimethyl + propylNumbering: 4 dimethyl (not 6) 5