Как получить 2,2,3,3-тетраметилбутан

Химия Органическая химия
26

@eudaimon this is still incomplete. Provide reactions leading to 2,2,3,3-tetramethylbutane from pivalic acid

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27

Apologies for the incomplete response earlier. Let’s continue from pivalic acid and provide the reactions leading to 2,2,3,3-tetramethylbutane.

Step 3 (continued): Formation of Pivalic Acid

\ce{(CH3)3CCN + 2 H2O ->[\text{H}^+] (CH3)3CCO2H + NH3}
  • Explanation: Acidic hydrolysis of tert-butyl cyanide converts the nitrile group to a carboxylic acid, yielding pivalic acid (2,2-dimethylpropanoic acid).

Step 4: Formation of Sodium Pivalate

\ce{(CH3)3CCO2H + NaOH -> (CH3)3CCO2Na + H2O}
  • Explanation: Pivalic acid reacts with sodium hydroxide to form sodium pivalate, the sodium salt of the carboxylic acid.

Step 5: Kolbe Electrolysis of Sodium Pivalate

\ce{2 (CH3)3CCO2Na ->[\text{Electrolysis}] (CH3)3C-C(CH3)3 + 2 CO2 + H2 + 2 NaOH}
  • Explanation: In the Kolbe electrolysis, sodium pivalate undergoes electrochemical decarboxylation at the anode, coupling the tert-butyl radicals to form 2,2,3,3-tetramethylbutane, along with carbon dioxide and hydrogen gas.

Overall Reaction Sequence

Starting from methane, the entire sequence of reactions is as follows:

  1. Chlorination of Methane

    \ce{CH4 + Cl2 -> CH3Cl + HCl}
    • Explanation: Radical chlorination forms methyl chloride.

  2. Formation of Acetylene (Ethyne)

    \ce{2 CH3Cl + 3 NaNH2 -> HC#CH + 3 NaCl + 3 NH3}
    • Explanation: Methyl chloride reacts with sodamide to form acetylene.

  3. Formation of tert-Butyl Alcohol via Acetylene

    a. Formation of Acetone

    \ce{HC#CH + H2O ->[\text{HgSO4/H2SO4}] CH3COCH3}
    • Explanation: Hydration of acetylene yields acetone (via enol-keto tautomerism).

    b. Formation of tert-Butyl Alcohol

    \ce{CH3COCH3 + CH3MgBr -> (CH3)3COH + MgBrOH}
    • Explanation: Grignard addition of methylmagnesium bromide to acetone forms tert-butyl alcohol.

  4. Conversion to tert-Butyl Chloride

    \ce{(CH3)3COH + HCl -> (CH3)3CCl + H2O}
    • As previously described.

  5. Formation of tert-Butyl Cyanide

    \ce{(CH3)3CCl + NaCN -> (CH3)3CCN + NaCl}
    • As previously described.

  6. Hydrolysis to Pivalic Acid

    \ce{(CH3)3CCN + 2 H2O ->[\text{H}^+] (CH3)3CCO2H + NH3}
    • As previously described.

  7. Formation of Sodium Pivalate

    \ce{(CH3)3CCO2H + NaOH -> (CH3)3CCO2Na + H2O}
    • As previously described.

  8. Kolbe Electrolysis to Form 2,2,3,3-Tetramethylbutane

    \ce{2 (CH3)3CCO2Na ->[\text{Electrolysis}] (CH3)3C-C(CH3)3 + 2 CO2 + H2 + 2 NaOH}
    • As previously described.

Final Product

The final product is 2,2,3,3-tetramethylbutane, obtained through the dimerization of the tert-butyl radicals during Kolbe electrolysis.

Alternative, Shorter Route

To achieve the synthesis more efficiently, consider the following streamlined pathway:

  1. From Methane to Isobutane

    a. Chlorination of Methane

    \ce{CH4 + Cl2 -> CH3Cl + HCl}

    b. Formation of Propane via Wurtz Reaction

    \ce{CH3Cl + 2 Na + ClCH2CH3 -> CH3CH2CH3 + 2 NaCl}
    • Explanation: React methyl chloride and ethyl chloride in a Wurtz reaction to form propane.

    c. Chlorination of Propane to 2-Chloropropane

    \ce{CH3CH2CH3 + Cl2 ->[\text{hv}] CH3CHClCH3 + HCl}

    d. Formation of Isobutane via Wurtz Reaction

    \ce{CH3Cl + 2 Na + ClCH(CH3)2 -> (CH3)3CH + 2 NaCl}

  2. Chlorination to tert-Butyl Chloride

    \ce{(CH3)3CH + Cl2 -> (CH3)3CCl + HCl}

  3. Formation of Sodium tert-Butoxide

    \ce{(CH3)3CCl + NaOH -> (CH3)3CONa + NaCl + H2O}

  4. Williamson Ether Synthesis to Form Di-tert-butyl Ether

    \ce{(CH3)3CCl + (CH3)3CONa -> (CH3)3COC(CH3)3 + NaCl}

  5. Cleavage of Ether to 2,2,3,3-Tetramethylbutane

    \ce{(CH3)3COC(CH3)3 + HI -> (CH3)3C-C(CH3)3 + H2O + I2}
    • Explanation: Di-tert-butyl ether reacts with hydroiodic acid to cleave the ether bond, forming 2,2,3,3-tetramethylbutane.

Conclusion

By carefully selecting reactions that build up the carbon skeleton, we can efficiently synthesize 2,2,3,3-tetramethylbutane from methane. The key steps involve forming suitable intermediates and utilizing reactions like the Wurtz reaction and Kolbe electrolysis to construct the desired molecule.

Feel free to ask if you need further clarification on any of the steps!

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