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Chapter 13: Problem 283

Outline all steps in a possible laboratory synthesis of each of the following, using benzene, toluene, and any needed aliphatic or inorganic reagents. (a) p-bromobenzyl chloride (b) triphenylchloromethane (c) allyl iodide (d) benzal bromide (e) \(\mathrm{m}\) -nitrobenzotrichloride (f) 1,2 -dichloro-1- phenylethane (g) phenylacetylene (h) phenylcyclopropane

Short Answer

Expert verified
(a) p-bromobenzyl chloride synthesis: 1. Friedel-Crafts Alkylation of benzene with 1-chloropropane (AlCl3 catalyst). 2. Bromination of propylbenzene (Br2, FeBr3 catalyst). 3. Chlorination of p-bromopropylbenzene (SOCl2). (b) triphenylchloromethane synthesis: 1. Friedel-Crafts Alkylation of benzene with chloroform (CHCl3, AlCl3 catalyst). (c) allyl iodide synthesis: 1. Preparation of allyl chloride (propene + Cl2). 2. Halogen exchange reaction (KI). (d) benzal bromide synthesis: 1. Gattermann-Koch reaction (benzene, CO, HCl, AlCl3, CuCl catalysts). 2. Bromination (benzaldehyde + PBr3). (e) m-nitrobenzotrichloride synthesis: 1. Nitration (benzene, HNO3, H2SO4). 2. Trichlorination (m-nitrobenzene, Cl2, AlCl3 or FeCl3 catalyst). (f) 1,2-dichloro-1-phenylethane synthesis: 1. Friedel-Crafts Alkylation (benzene, 1,2-dichloroethane, AlCl3 catalyst). (g) phenylacetylene synthesis: 1. Birch reduction (benzene, Na, NH3, ethanol). 2. Bromination (1,4-cyclohexadiene, NBS). 3. Corey-Fuchs reaction (1-bromo-4-cyclohexene, PPh3, CCl4). (h) phenylcyclopropane synthesis: 1. Simmons-Smith reaction (styrene, CH2I2, Zn-Cu couple catalyst).

Step by step solution

01

(a) p-bromobenzyl chloride synthesis

1. Friedel-Crafts Alkylation: React benzene with 1-chloropropane in the presence of an aluminum chloride catalyst (AlCl3) to form propylbenzene. 2. Bromination: React propylbenzene with bromine (Br2) and iron(III) bromide (FeBr3) catalyst to form p-bromopropylbenzene. 3. Chlorination: React p-bromopropylbenzene with thionyl chloride (SOCl2) to replace the bromine with a chlorine atom, resulting in the final product, p-bromobenzyl chloride.
02

(b) triphenylchloromethane synthesis

1. Friedel-Crafts Alkylation: React benzene with chloroform (CHCl3) and anhydrous aluminum chloride (AlCl3) as a catalyst to produce triphenylchloromethane.
03

(c) allyl iodide synthesis

1. Preparation of allyl chloride: React propene with Cl2 to form allyl chloride. 2. Halogen exchange reaction: Treat the allyl chloride with potassium iodide (KI) to produce allyl iodide.
04

(d) benzal bromide synthesis

1. Gattermann-Koch reaction: React benzene with carbon monoxide (CO) and hydrogen chloride (HCl) in the presence of an aluminum chloride (AlCl3) and cuprous chloride (CuCl) catalyst to form benzaldehyde. 2. Bromination: Treat benzaldehyde with phosphorus tribromide (PBr3) to form benzal bromide.
05

(e) m-nitrobenzotrichloride synthesis

1. Nitration: Treat benzene with nitric acid (HNO3) and sulfuric acid (H2SO4) to form m-nitrobenzene. 2. Trichlorination: Treat m-nitrobenzene with chlorine (Cl2) and a Lewis acid catalyst such as aluminum chloride (AlCl3) or iron(III) chloride (FeCl3) to form m-nitrobenzotrichloride.
06

(f) 1,2-dichloro-1-phenylethane synthesis

1. Friedel-Crafts Alkylation: React benzene with 1,2-dichloroethane and aluminum chloride (AlCl3) catalyst to form 1,2-dichloro-1-phenylethane.
07

(g) phenylacetylene synthesis

1. Birch reduction: Reduce benzene to 1,4-cyclohexadiene using sodium metal (Na) and liquid ammonia (NH3) in the presence of an alcohol, such as ethanol. 2. Bromination: React 1,4-cyclohexadiene with N-bromosuccinimide (NBS) to form 1-bromo-4-cyclohexene. 3. Corey-Fuchs reaction: Treat the 1-bromo-4-cyclohexene with two equivalents of triphenylphosphine (PPh3) and one equivalent of carbon tetrachloride (CCl4) to form phenylacetylene.
08

(h) phenylcyclopropane synthesis

1. Simmons-Smith reaction: React styrene (vinylbenzene) with diiodomethane (CH2I2) and a zinc-copper couple catalyst to form phenylcyclopropane.

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Most popular questions from this chapter

Give the structures and names of the chief organic products expected from the reaction (if any) of n-butyl bromide with: (a) \(\mathrm{NaOH}(\mathrm{aq})\) (g) product (f) \(+\mathrm{D}_{2} \mathrm{O}\) (b) \(\mathrm{KOH}(\mathrm{alc})\) (h) dilute neutral \(\mathrm{KMnO}_{4}\) (c) cold conc. \(\mathrm{H}_{2} \mathrm{SO}_{4}\) (i) Nal in acetone (d) \(\mathrm{Zn}, \mathrm{H}^{+}\) (i) \(\mathrm{HC} \equiv \mathrm{C}^{-} \mathrm{Na}^{+}\) (e) Li, then Cul, ethyl bromide (f) \(\mathrm{Mg}\), ether (k) \(\mathrm{H}_{2} \mathrm{O}\) (1) \(\mathrm{NH}_{3}(\mathrm{aq})\)

Draw a reaction coordinate diagram for the solvolysis of \(2,2,2\) -triphenylethyl chloride in acetic acid. Pay special attention to the phenonium-ion intermediate. What would be the difference in this diagram if the phenonium ion were a transition state instead of an intermediate?

HCN has \(\mathrm{pK}_{\mathrm{a}}=9.21 ;\) acetic acid has \(\mathrm{pK}_{\mathrm{a}}=4.76 .\) (a) What is the difference in the standard free energies \(\left(\Delta \Delta \mathrm{G}^{\circ}\right)\) for these two acid-base equilibria? (b) What is the equilibrium constant and \(\Delta \mathrm{G}^{\circ}\) for the reaction \(\mathrm{HCN}+\mathrm{CH}_{3} \mathrm{CO}_{2}^{-} \rightarrow \mathrm{CN}^{-}+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\)

Each of the following might have been synthesized by an \(\mathrm{S}_{\mathrm{N}} 2\) reaction. Suggest a combination of substrate and nucleophile which could have led to their production.

Under \(\mathrm{S}_{\mathrm{N}} 1\) conditions, 2 -bromo octane, of specific rotation \(-20.8^{\circ}\), was found to yield 2 -octanol of specific rotation \(+3.96^{\circ}\). If optically pure 2-bromooctane has a specific rotation of \(-34.6^{\circ}\) and optically pure 2-octanol has a specific rotation of \(-9.9^{\circ}\) calculate: (a) the optical purity of reactant and product; (b) the percentage of racemization and of inversion accompanying the reaction; (c) the percentage of front side and of back side attack on the carbonium ion.
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