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Chapter 11 Unsaturated Hydrocarbons. 11.1 Alkenes and Alkynes. Saturated Hydrocarbons. Saturated hydrocarbons have the maximum number of hydrogen atoms attached to each carbon atom. are alkanes and cycloalkanes with single C-C bonds. CH 3 —CH 2 —CH 3. Unsaturated Hydrocarbons.
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Chapter 11 Unsaturated Hydrocarbons 11.1 Alkenes and Alkynes
Saturated Hydrocarbons Saturated hydrocarbons • have the maximum number of hydrogen atoms attached to each carbon atom. • are alkanes and cycloalkanes with single C-C bonds. CH3—CH2—CH3
Unsaturated Hydrocarbons Unsaturated hydrocarbons • have fewer hydrogen atoms attached to the carbon chain than alkanes. • are alkenes with double bonds. • are alkynes with triple bonds.
Bond Angles in Alkenes and Alkynes According to VSEPR theory: • the three groups bonded to carbon atoms in a double bond are at 120° angles. • alkenes are flat because the atoms in a double bond all lie in the same plane. • the two groups bonded to each carbon in a triple bond are at 180° angles.
Naming Alkenes The names of alkenes • use the corresponding alkane name. • change the ending to –ene. Alkene IUPAC Common H2C=CH2 ethene ethylene H2C=CH─CH3 propenepropylene cyclohexene
Ethene (Ethylene) Ethene or ethylene • is an alkene with the formula C2H4. • has two carbon atoms connected by a double bond. • has two H atoms bonded to each C atom. • is flat with all the C and H atoms in the same plane. • is used to accelerate the ripening of fruits.
Naming Alkynes The names of alkynes • use the corresponding alkane name. • change the ending to –yne. Alkyne IUPAC Common HC≡CH ethyne acetylene HC≡C─CH3 propyne
Naming Alkenes and Alkynes When the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond. CH2=CH─CH2─CH3 1-butene 1 2 3 4 CH3─CH=CH─CH3 2-butene 1 2 3 4 CH3─CH2─CC─CH3 2-pentyne 5 4 3 2 1
Learning Check Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH3 2. CH3─CH=CH─CH3 CH3 | 3. CH3─CH=C─CH3 4. CH3─CC─CH3
Solution Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH31-butene 2. CH3─CH=CH─CH32-butene CH3 | 3. CH3─CH=C─CH32-methyl-2-butene 4. CH3─CC─CH32-butyne
Learning Check Write the IUPAC name for each of the following: A. CH3─CH2─C≡C─CH3 CH3 B. CH3─CH2─C=CH─CH3
Solution Write the IUPAC name for each of the following: A. CH3─CH2─C≡C─CH3 2-pentyne CH3 B. CH3─CH2─C=CH─CH3 3-methyl-2-pentene