Name Reactions & Conversions

CHEName Reactions & Conversions

This subtopic is about multi-step synthesis — converting one functional group into another and identifying intermediates in a reaction sequence. Success depends on knowing each reagent and condition precisely and chaining them in the right order.

Phenol from chlorobenzene (Dow)

C_6H_5Cl + NaOH \xrightarrow[\text{high } P]{623\ K} C_6H_5ONa \xrightarrow{H^+} C_6H_5OH

Propan-2-ol to propan-1-ol

CH_3CH(OH)CH_3 \xrightarrow{\text{conc. } H_2SO_4} CH_3CH{=}CH_2 \xrightarrow{B_2H_6;\ H_2O_2,\ OH^-} CH_3CH_2CH_2OH

Ethanol to butane (Wurtz)

2\,C_2H_5I + 2Na \xrightarrow{\text{dry ether}} C_4H_{10} + 2NaI

Ethanol to ethyl acetate

C_2H_5OH + CH_3COOH \rightleftharpoons CH_3COOC_2H_5 + H_2O

Benzene $\rightarrow$ phenol routes: cumene process, Dow process (chlorobenzene + NaOH, high T/P), or via diazonium salt ( $C_6H_5N_2^+$ , warm water).
Anisole from sodium phenoxide: $C_6H_5O^-Na^+ + CH_3I \rightarrow C_6H_5OCH_3$ (Williamson, $S_N2$ ).
Propan-2-ol $\rightarrow$ propan-1-ol: dehydrate to propene (conc. $H_2SO_4$ ), then hydroboration–oxidation ( $B_2H_6$ ; $H_2O_2$ / $OH^-$ , anti-Markovnikov).
Propene $\rightarrow$ propan-2-ol: acid-catalysed (Markovnikov) hydration with dil. $H_2SO_4$ / $H_2O$ .
Cumene sequence: cumene $\xrightarrow{O_2}$ A (cumene hydroperoxide) $\xrightarrow{H_2SO_4}$ B (phenol) + C (acetone); then phenol $\xrightarrow{Br_2/H_2O}$ D (2,4,6-tribromophenol).
Ethanol $\rightarrow$ diethyl ether (conc. $H_2SO_4$ , $413\,\text{K}$ ); $\rightarrow$ ethyl acetate ( $CH_3COOH$ , conc. $H_2SO_4$ , esterification).
Ethanol $\rightarrow$ butane: convert to $C_2H_5I$ (with HI or red $P/I_2$ ), then Wurtz reaction ( $2\,C_2H_5I + 2Na \rightarrow C_4H_{10} + 2NaI$ ).
Anisole from phenol and methanol: convert phenol to sodium phenoxide (NaOH), then react with $CH_3I$ (or $(CH_3)_2SO_4$ ); direct phenol $+ CH_3OH$ does not give a clean Williamson product.
Phenol $\rightarrow$ salicylic acid (Kolbe) and phenol $\rightarrow$ salicylaldehyde (Reimer–Tiemann) are the two named phenol conversions most often chained into sequences.
Alcohol $\rightarrow$ aldehyde/ketone: controlled oxidation (PCC, or Cu/ $573\,\text{K}$ ); aldehyde/ketone $\rightarrow$ alcohol: $NaBH_4$ or $LiAlH_4$ — useful for interconverting $1^\circ$ and $2^\circ$ alcohols.
Ascending/descending the chain: Grignard with $HCHO$ adds one carbon to give a $1^\circ$ alcohol; the Wurtz reaction doubles the carbon skeleton (used in ethanol $\rightarrow$ butane).
Ethanol $\rightarrow$ ethene (conc. $H_2SO_4$ , $443\,\text{K}$ ) is the gateway to many alkene-based conversions (addition of $Br_2$ , HBr, etc.).

Where the marks go

Trying to make propan-1-ol from propene by acid hydration — that gives propan-2-ol; the $2^\circ \rightarrow 1^\circ$ switch needs dehydration then anti-Markovnikov hydroboration.
Reacting phenol directly with methanol for anisole — first make the phenoxide; the nucleophile is $C_6H_5O^-$ , and the alkylating agent must be $CH_3I$ / $(CH_3)_2SO_4$ , not $CH_3OH$ .
Mixing up the cumene intermediates — A is cumene hydroperoxide, B is phenol, C is acetone; labelling acetone as the main product instead of phenol loses marks.
Forgetting Wurtz needs an alkyl halide and dry ether — ethanol must first be turned into $C_2H_5I$ ; sodium does not couple alcohols directly.
Writing esterification as irreversible — it is a reversible equilibrium needing conc. $H_2SO_4$ as catalyst and dehydrating agent; show the double arrow.

How the board asks it

Conversionmulti-step functional-group interconversions (propan-2-ol $\to$ propan-1-ol via dehydration then hydroboration; ethanol $\to$ butane via $C_2H_5I$ then Wurtz; phenol $\to$ anisole via sodium phenoxide)
How will you convert: (i) propan-2-ol into propan-1-ol, (ii) ethanol into butane, and (iii) phenol into anisole? Give the reagents and conditions for each step.
Identify / classifythe cumene-process sequence intermediates ( $A$ = cumene hydroperoxide, $B$ = phenol, $C$ = acetone, $D$ = $2,4,6$ -tribromophenol)
In the sequence cumene $\xrightarrow{O_2} A \xrightarrow{H_2SO_4} B + C$ , then $B \xrightarrow{Br_2/H_2O} D$ , identify the compounds $A$ , $B$ , $C$ and $D$ .
Predict the productreagent-and-condition specificity for ethanol with conc. $H_2SO_4$ ( $413\,\text{K}$ gives diethyl ether, $443\,\text{K}$ gives ethene)
Give the structure of the major organic product, with a balanced equation, when ethanol is heated with conc. $H_2SO_4$ at $443\,\text{K}$ , and separately at $413\,\text{K}$ .
Give reasonsthe propene-hydration regiochemistry (Markovnikov vs anti-Markovnikov) and the phenoxide requirement for anisole
Account for the following: (i) propan-1-ol cannot be obtained from propene by acid-catalysed hydration, and (ii) anisole is not prepared by directly heating phenol with methanol.
Mechanismthe Williamson ether synthesis ( $S_N2$ ) of anisole from sodium phenoxide
Write the mechanism for the formation of anisole from sodium phenoxide and methyl iodide ( $CH_3I$ ), indicating the nucleophile and the type of substitution involved.
Distinguishthe two named phenol conversions (Kolbe gives salicylic acid; Reimer–Tiemann gives salicylaldehyde)
Distinguish between the Kolbe reaction and the Reimer–Tiemann reaction of phenol, naming the principal product and the reagents in each case.

Practise this topic

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Written for Sublevo. Question text quoted anywhere in these notes is the Council’s and carries its year and paper; the board’s own diagrams are not reproduced.