子路
Lv 6
子路 asked in 科學及數學化學 · 1 decade ago

homolysis and hereolysis

when the following substances dissolve in water, explain whether it is a homolysis or heterolysis

i) CH3COOH

ii) CH3CH2OH

1 Answer

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  • 莫愁
    Lv 6
    1 decade ago
    Favorite Answer

    For both (i) and (ii), they will carry out heterolytic reaction instead. For

    hemolytic reaction to occur, there are several criteria:

    (a)the electronegative between the covalent bond should be similar.

    (b)There should be a benzyl peroxide or hydrogen peroxide presence

    (c)Heat energy should always be supplied.

    For (a)you will find example in polymerization and decolourization of

    methane in the presence of diffused sunlight. In those reactions, the atoms

    involved are carbon bonded by single or double covalent bond(s) in which

    the electronegativities between carbon-carbon atoms in the polymerization

    of ethene are similar. For C the Pauli scaling is 2.6. The difference between

    C and C is 0. And for decolourization of methane ,the difference between C

    and H is just very little 0.4 (For O the Pauli scaling is 2.6.) You can compare

    this value (0.4) with heterolytic one.

    For (b) you will find example in polymerization of ethene which requires a

    peroxide to initialize the reaction.

    For (c)you will find example in catalytic cracking with the aim of

    producing more alkene sources and giving more petroleum products.

    During this process, the covalent bonds are broken homolytically due to

    the vigorous vibrations within molecules and free radicals will form.

    The formed free radicals will rearrange themselves again to give new

    source of alkenes.

    For heterolytic reaction, it occurs within covalent bonds where the

    electronegativities between atoms are quite difference such as O and H

    atom.For example, ethanoic acid dissolves in water to give hydrogen ions.

    For O, the Pauli scaling is 3.5 and for H is 2.2. The difference between O

    and H is 1.3. The difference is large comparing hemolytic one.

    Besides, temperature involved should be low such as at room temperature.

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