Question

Show how to prepare each compound from 1-heptene. (a) 1,2 -Dichloroheptane (b) 1 -Heptyne (c) 1-Heptanol (d) 2-Octyne (e) cis-2-Octene (f) trans-2-Octene

Short answer

Question: Describe the process of converting 1-heptene into the following compounds: (a) 1,2-Dichloroheptane, (b) 1-Heptyne, (c) 1-Heptanol, (d) 2-Octyne, (e) cis-2-Octene, and (f) trans-2-Octene. Answer: (a) React 1-heptene with Cl2 in the presence of CCl4 as solvent to form 1,2-dichloroheptane via halogenation. (b) First, convert 1-heptene to 1-bromoheptane via hydrohalogenation with HBr. Then, treat 1-bromoheptane with two moles of NaNH2 to form 1-heptyne. (c) Convert 1-heptene to 1-heptanol by performing an acid-catalyzed hydration reaction using water (H2O) and an acid catalyst such as H2SO4. (d) First, react 1-heptene with a Wittig reagent (Ph3P=CH2) to form 1-hepten-1-yl(triphenyl)phosphonium salt, and then perform an intramolecular Wittig reaction using BuLi to generate 2-octyne. (e) Perform chain elongation on 1-heptene using Wittig reagent (Ph3P=CH2) and BuLi to generate 2-octene. Then, selectively convert 2-octene to cis-2-octene using Lindlar's catalyst (Pd/BaSO4) and a hydrogen source (H2). (f) Perform chain elongation on 1-heptene using Wittig reagent (Ph3P=CH2) and BuLi to generate 2-octene. Then, isomerize cis-2-octene to trans-2-octene by heating in the presence of a suitable catalyst such as KOtBu (potassium tert-butoxide).

Step-by-step solution

(a) Synthesis of 1,2-Dichloroheptane from 1-heptene

Step 1: Addition of Cl2 using Halogenation React 1-heptene with Cl2 to form a 1,2-dichloroheptane via halogenation in the presence of carbon tetrachloride (CCl4) as solvent. The balanced reaction equation is: C7H14 (1-heptene) + Cl2 -> C7H12Cl2 (1,2-dichloroheptane)

(b) Synthesis of 1-Heptyne from 1-heptene

Step 1: Hydrohalogenation for Intermediate HBr reagent To convert 1-heptene to 1-heptyne, first form 1-bromoheptane by adding HBr to the double bond. C7H14 (1-heptene) + HBr -> C7H15Br (1-bromoheptane) Step 2: Elimination reaction using NaNH2 for final product Treat the formed 1-bromoheptane with two moles of NaNH2, an extremely strong base, to form one mole of 1-heptyne: 2 NaNH2 + C7H15Br (1-bromoheptane) -> C7H12 (1-heptyne) + 2 NaBr + 2 NH3

(c) Synthesis of 1-Heptanol from 1-heptene

Step 1: Hydration reaction to form alcohol To convert 1-heptene to 1-heptanol, perform an acid-catalyzed hydration reaction with water (H2O) and any suitable acid as catalyst, such as H2SO4: C7H14 (1-heptene) + H2O -> C7H16O (1-heptanol) + H2SO4 (catalyst)

(d) Synthesis of 2-Octyne from 1-Heptene

Step 1: Perform Chain Elongation First, react 1-heptene with a Wittig reagent, Ph3P=CH2, in order to form 1-hepten-1-yl(triphenyl)phosphonium salt; Next, perform an intramolecular Wittig reaction by adding BuLi. This will form 2-octyne.

(e) Synthesis of cis-2-Octene from 1-heptene

Step 1: Perform Chain Elongation (similar to previous step 1) Follow the same procedure, using Wittig reagent Ph3P=CH2 and BuLi, to generate 2-octene. Step 2: Generate cis-2-octene Treat 2-octene with Lindlar's catalyst (Pd/BaSO4) and a hydrogen source (H2) to obtain cis-2-octene selectively.

(f) Synthesis of trans-2-Octene from 1-heptene

Step 1: Perform Chain Elongation (similar to previous step 1) Follow the same procedure, using Wittig reagent Ph3P=CH2 and BuLi, to generate 2-octene. Step 2: Generate trans-2-octene Perform alkene isomerization from cis to trans, by heating the cis-2-octene in the presence of a suitable catalyst, such as KOtBu (potassium tert-butoxide). This will activate the double bond and produce trans-2-octene.