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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 isomers- structural/ constitutional isomers: compounds having the same molecular structure but different structural formulas- C4H10 has 2 isomers – butane straight chain, & 2-methl-propane (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-ALKYNES- 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 -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 (octane number 0) and 2,2,4-trimethylpentane (octane number 100)- percentage of 2,2,4-trimethylpentane in the comparison mixture thatexactly matches the performance of a gasoline is the octane number ofthat gasoline- ex: gasoline that performs like mixture containing 88% 2,2,4-trimethylpentane and 12% heptane has an octane 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


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DREXEL CHEM 103 - Exam 1 Outline

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