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Show how 1-pentanol could be transformed into each of the following compounds by completing the given syntheses.

(a) 2-Bromopentane

(b) 1-Hexanol

(c) 4-Methyl-4-nonanol

1 Answer

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Answer:

Step-by-step explanation:

(a) Synthesis of 2-Bromopentane from 1-Pentanol:

Step 1: Convert 1-Pentanol to 1-Bromopentane

1-Pentanol can be converted to 1-Bromopentane by reacting it with hydrogen bromide (HBr) in the presence of sulfuric acid (H2SO4) as a catalyst.

CH3CH2CH2CH2CH2OH + HBr → CH3CH2CH2CH2CH2Br + H2O

Step 2: Rearrange to Get 2-Bromopentane

To obtain 2-Bromopentane, heat the 1-Bromopentane with an alkoxide ion like sodium ethoxide (CH3CH2ONa). This rearrangement is called an E2 elimination reaction.

CH3CH2CH2CH2CH2Br + CH3CH2O^-Na+ → CH3CH2CH2CH2CH2CH2CH2O^- + NaBr

CH3CH2CH2CH2CH2CH2CH2O^- → CH3CH2CH2CH2CH2CH2CH2H + CH3CH2CH=CH2

The final product is 2-Bromopentane.

(b) Synthesis of 1-Hexanol from 1-Pentanol:

Step 1: Oxidation of 1-Pentanol to Obtain 1-Pentanal

1-Pentanol is oxidized to 1-Pentanal using an oxidizing agent like potassium dichromate (K2Cr2O7) and sulfuric acid (H2SO4).

CH3CH2CH2CH2CH2OH + [O] → CH3CH2CH2CH2CH2CHO

Step 2: Reduce 1-Pentanal to 1-Hexanol

1-Pentanal is then reduced to 1-Hexanol using a reducing agent like sodium borohydride (NaBH4).

CH3CH2CH2CH2CH2CHO + NaBH4 → CH3CH2CH2CH2CH2CH2OH

The final product is 1-Hexanol.

(c) Synthesis of 4-Methyl-4-nonanol from 1-Pentanol:

Step 1: Convert 1-Pentanol to 1-Bromopentane

Follow the same procedure as described in part (a) to convert 1-Pentanol to 1-Bromopentane.

CH3CH2CH2CH2CH2OH + HBr → CH3CH2CH2CH2CH2Br + H2O

Step 2: Grignard Reaction to Obtain 4-Methyl-4-nonanol

React the 1-Bromopentane with methylmagnesium bromide (CH3MgBr) in an ether solvent to form a Grignard reagent. Then, react the Grignard reagent with n-nonanal.

CH3CH2CH2CH2CH2Br + CH3MgBr → CH3CH2CH2CH2CH2CH2CH2CH2MgBr

CH3CH2CH2CH2CH2CH2CH2CH2MgBr + H3C-CO-CH2-CH2-CH2-CH2-CH2-CH2-CH2 → CH3CH2CH2CH2CH2CH2CH2CH2CH2-CO-CH2-CH2-CH2-CH2-CH2-CH2-CH2CH3

The final product is 4-Methyl-4-nonanol.

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