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SolutionsNomenclature

1. Name the compounds

Name the following compounds:

Eight alkenes to name: a) tetrasubstituted alkene with ethyl, propyl and two methyl groups; b) dimethylcyclopentene; c) diene with two methyl groups; d) tert-butylcyclohexene; e) isopropylmethylcyclohexene; f) terminal alkene with methyl and ethyl; g) methylcycloheptene; h) trimethylcyclopentene
Structures of the eight alkenes with their names in English and Spanish
  1. (3E)-3,4-dimethylhept-3-ene
  2. 1,3-dimethylcyclopentene
  3. 4,5-dimethylhexa-1,4-diene
  4. (3R)-3-tert-butylcyclohexene
  5. (3R)-3-isopropyl-1-methylcyclohexene
  6. 2-methylbut-1-ene
  7. 1-methylcycloheptene
  8. 1,4,4-trimethylcyclopentene

2. Write the structure

  1. (Z)-3-Methylpent-2-ene
  2. trans-1,2-Dichloroethene
  3. 3-Ethylpenta-1,4-diene
  4. 2-Methyl-1-methylidenecyclohexane
  1. CH3CH=C(CH3)CH2CH3, with the CH3 on C2 and the ethyl on C3 on the same side (they are the higher-priority groups on each carbon).
  2. ClCH=CHCl with the two chlorines on opposite sides; it is also called (E)-1,2-dichloroethene.
  3. CH2=CH–CH(CH2CH3)–CH=CH2.
  4. A cyclohexane with an exocyclic =CH2 on C1 and a methyl group on C2.

3. E or Z?

Say which group has priority on each carbon of the double bond and what the Z isomer looks like for: a) CH3CH2C(CH3)=CHCH3; b) BrCH=C(Cl)CH3; c) (CH3)2CHC(CH2OH)=CHCH3.

  1. On C3 ethyl has priority over methyl; on C2, CH3 over H: the Z isomer has the ethyl and that CH3 on the same side.
  2. On C1 Br has priority over H and on C2 Cl over CH3: it is Z if Br and Cl are on the same side.
  3. On C3 the CH2OH (C bonded to O) has priority over the isopropyl (C bonded to C, C, H): it is Z if the CH2OH and the CH3 on C2 are on the same side.

The Cahn-Ingold-Prelog rules are applied to each carbon of the double bond separately: the atomic numbers of the directly bonded atoms are compared and, if they are equal, those of the next atoms.

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