jackdiamond24
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Hi so I just had my AS mock, and one of the big 7 markers was with organic mechanisms. From what I remember, it asked for the mechanism of the reaction between ICl and CH4, and it said that this reaction is similar to that of Cl2 and CH4 (free radical subtitution - which is what we have learnt and is on the specification). the first question asked what was needed to get the reaction started --> UV light. But here is where I am confused, homolytic fission is when the bond between two atoms of the same electronegativity is broken, and so electrons are shared equally and the Cl2 would turn into 2 Cl radicals. However, during the exam I knew that Fluorine is much more electronegative than Iodine, and so I thought this would be heterolytic fission and the Fluorine would take both of the electrons form the bond. Hence it asked for the mechanism, which turned out to be completely different than that of the free radical substitution reaction of Cl2 and CH4.

So please tell me, is this an example of free radical substitution, the same as Chlorine, or is it something else
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Maz A
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(Original post by jackdiamond24)
Hi so I just had my AS mock, and one of the big 7 markers was with organic mechanisms. From what I remember, it asked for the mechanism of the reaction between ICl and CH4, and it said that this reaction is similar to that of Cl2 and CH4 (free radical subtitution - which is what we have learnt and is on the specification). the first question asked what was needed to get the reaction started --> UV light. But here is where I am confused, homolytic fission is when the bond between two atoms of the same electronegativity is broken, and so electrons are shared equally and the Cl2 would turn into 2 Cl radicals. However, during the exam I knew that Fluorine is much more electronegative than Iodine, and so I thought this would be heterolytic fission and the Fluorine would take both of the electrons form the bond. Hence it asked for the mechanism, which turned out to be completely different than that of the free radical substitution reaction of Cl2 and CH4.

So please tell me, is this an example of free radical substitution, the same as Chlorine, or is it something else
The electrons are shared so the homolytic fission occurs in which we get tow free radicles Cl2-->2Cl^ [^ is unpaired electron]. Cl^+CH4-->CH3^+HCl. CH3^+Cl2-->CH3Cl^+Cl^. Termination: Cl^+Cl^-->Cl2. CH3^+CH3^-->C2H6. SO it follows the same pattern hope this helped a bit, check out chemguide which I found useful (i have my mock tomorrow).
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jackdiamond24
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(Original post by Maz A)
The electrons are shared so the homolytic fission occurs in which we get tow free radicles Cl2-->2Cl^ [^ is unpaired electron]. Cl^+CH4-->CH3^+HCl. CH3^+Cl2-->CH3Cl^+Cl^. Termination: Cl^+Cl^-->Cl2. CH3^+CH3^-->C2H6. SO it follows the same pattern hope this helped a bit, check out chemguide which I found useful (i have my mock tomorrow).
Hi so of course that is the typical free radical substitution mechanism that we should know and i understand it, however the question was about Iodine monochloride and Methane, not Chlorine and Methane, I'm asking if when Iodine and Chlorine are split, is it homolytic or heterolytic fission as they are not the same elements and have a difference in electronegativity. Because Chlorine is much more electronegative than Iodine, I reckon Chlorine would take both of its electrons. This was a 7 mark question so i'm really worried!
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Maz A
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(Original post by jackdiamond24)
Hi so of course that is the typical free radical substitution mechanism that we should know and i understand it, however the question was about Iodine monochloride and Methane, not Chlorine and Methane, I'm asking if when Iodine and Chlorine are split, is it homolytic or heterolytic fission as they are not the same elements and have a difference in electronegativity. Because Chlorine is much more electronegative than Iodine, I reckon Chlorine would take both of its electrons. This was a 7 mark question so i'm really worried!
Ah ok my apologies, at first glance it does look like heterolytic fission but yeah we haven't focused on a case like that in class so sorry, I'm sure your teacher will tell you though, good luck.
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jackdiamond24
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(Original post by Maz A)
Ah ok my apologies, at first glance it does look like heterolytic fission but yeah we haven't focused on a case like that in class so sorry, I'm sure your teacher will tell you though, good luck.
Thanks anyways, and yeah we haven't focused on a case like that either so that's why i'm so confused!
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