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Topic: Alkenes & Alkynes (unsaturated hydrocarbons). Do Now: Name the following. Are the Isomers?. Unsaturated hydrocarbons : organic compounds containing one or more double or triple bonds – can add more H by breaking the bond. Alkenes. Another homologous series of hydrocarbons
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Topic: Alkenes & Alkynes (unsaturated hydrocarbons) Do Now: Name the following. Are the Isomers?
Unsaturatedhydrocarbons: organic compounds containing one or more double or triple bonds – can add more H by breaking the bond
Alkenes • Another homologous series of hydrocarbons • Each member contains at least one double covalent bond between C atomsSo alkenes are unsaturated • General formula = CnH2n
Properties of Alkenes • Nonpolar – low solubility in H2O • fairly low melting and low boiling points • More reactive than alkanes : • double bond is site of reactivity
1st member is C2H4: ethene H H C=C H H Naming Alkenes • Count longest carbon chain • prefix tells # of C’s in longest chain and add ‘ene’
If more than 4 Carbons • give 1st carbon in double bond the lowest possible number when numbering the chain ] 1-butene 2-butene
If 2 double bonds = diene 1,3 pentadiene
Naming Branched-Chain Alkenes • 1st carbon in Double bond gets lowest number • Then name branches based on numbers assigned • Branch name and number come first when naming • Chain + ene come at the end • Example: 2-methyl 3-Nonene
3 methyl, 1-butene 4 3 2 1
Alkynes • Homologous series of unsaturated hydrocarbons • Each member contains at least one C≡C bond • General formula = CnH2n-2
Properties of Alkynes • Nonpolar – low solubility in H2O • fairly low melting and low boiling points • More reactive than alkenes : • triple bond is site of reactivity
Naming Alkynes • Same as alkene just add ‘yne’ to the end instead
H–CC–H C2H2 ethyne CHCH H H–CC–C–H H propyne C3H4 CHCCH3 CHCCH2CH3 1-butyne C4H6 C4H6 2-butyne CH3CCCH3 H H H–CC–C–C–H H H H H H–C–CC–C–H H H
Name of Series General Formula Ending Alkanes CnH2n+2 -ane Alkenes CnH2n -ene Alkynes CnH2n-2 -yne 3 Homologous Series of HC’s
Which compound belongs to the alkene series? • C2H2 • C2H4 • C6H6 • C6H14 Correct answer = B Alkenes follow the format CnH2n A & C are CnHn , D is CnH2n+2
In which group could the hydrocarbons all belong to the same homologous series? • C2H2, C2H4, C2H6 • C2H4, C3H4, C4H8 • C2H4, C2H6, C3H6 • C2H4, C3H6, C4H8 Correct answer = D Members of homologous series all have same relationship between atoms Every compound in set D fits the formula CnH2n
Which of the following is a saturated hydrocarbon? • Ethene • Ethyne • Propene • Propane Correct answer = D all alkanes are saturated