Chem 103 Exam 1 Outline ALKANES common facts CnH2n 2 methane is 85 natural gas butane propane are fuels alkanes are saturated all alkanes with more than 3 carbons have at least 2 structural structural constitutional isomers compounds having the same molecular structure but different structural formulas C4H10 has 2 isomers butane straight chain 2 methl propane isomers branched alkyl groups methyl ethyl propyl isopropyl butyl sec butyl t butyl iso butyl attached to second carbon iso means branched CH3 on next to last carbon second carbon n butane and n pentane are the normal long chained hydrocarbons tetrahedral angle is 109 5 deg cyclopentane and cyclohexane are the most abundant and most stable cyclohexane is not planar or flat in real life it makes a boat and chair shape chair form is more stable because the H s are farther away cycloalkanes are highly flammable properties of alkanes insoluble in water because hydrocarbons are NP and water is P physical state depends on number of carbons 1 to 4 gas 5 to 17 liquid 18 solid density is less than 1 g mL chemical combustion alkane oxygen carbon dioxide water heat halogens fluoro chloro iodo bromo halogenated hydrocarbons good solvents not very reactive not flammable toxic common names to know chloromethane is methyl chloride dichloromethane is methylene chloride trichloromethane is chloroform tetrachloromethane is carbon tetrachloride 2 bromo 2 chloro 1 1 1 trifluroethane general anesthetic ALKENES CnH2n alkenes are unsaturated because they contain multiple bonds ethene is ethylene propene is propylene etc just different names geometric isomers same molecular formula same structural formula cis trans is put in front of the IUPAC name to establish which one it is cis trans are important because they have different physical properties Markovikov s rule the Hydrogen atom goes to the double bonded carbon atom that already has the most Hydrogen atoms functional group atom or group of atoms that determines the properties of a molecule alkene functional group is the double bond alkene hydrogen alkane this is called hydrogenation halogenation of alkenes is fast and doesn t require catalyst in the Baeyer test if the red color disappears it s an alkene if it stays it is an alkane CnH2n 2 ethyne acetylene propyne methylacetylene 1 butyne ethylacetylene 2 butyne dimethylacetylene properties physical similar to alkanes and alkenes chemical similar to alkenes alkynes undergo addition alkynes are unsaturated because they contain multiple bonds ethyne is commonly known as acetylene ALKYNES BENZENE empirical formula CH molecular formula C6H6 ring is stable and unreactive bonds are resonating toluene benzene with methyl group methylbenzene nitrobenzene benzene with an NO2 group similarly chlorobenzene is benzene with a Cl attached xylene benzene with 2 methyl groups attached ortho 1 2 meta 1 3 para 1 4 o xylene m xylene p xylene xylene s full name is dimethylbenzene 1 4 dichlorobenzene p dichlorobenzene moth balls properties of benzene like other hydrocarbons density 1 g mL 2 4 6 trinitrotoluene is TNT PETROLEUM octane number isooctane is isooctane heptane mixture that gives the same performance as gasoline octane number rating system compares the performance of a gasoline with that of a mixture of 2 compounds heptane number 0 and 2 2 4 trimethylpentane octane number percentage of 2 2 4 trimethylpentane in the comparison mixture that exactly matches the performance of a gasoline is the octane number of that gasoline ex gasoline that performs like mixture containing 88 2 2 4 trimethylpentane and 12 heptane has an octane octane 100 number 88 crude petroleum is refined by distillation which is when different hydrocarbons are separated into fractions with similar boiling points and molecular sizes best gasoline is composed of highly branched alkanes which are not common in nature how to increase octane number add compounds with high octane numbers highly branched alkenes aromatics alcohols add antiknock agent look for soluble in gas cheap okay for environment