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Topic: alkenes and aldehydes  (Read 7229 times)

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Offline fran008

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alkenes and aldehydes
« on: February 27, 2006, 05:10:22 AM »
Can alkenes react with HCN and can aldehydes react with HBr. Why or why not?
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Offline Albert

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Re:alkenes and aldehydes
« Reply #1 on: February 27, 2006, 08:19:22 AM »
Generally speaking, alkenes cannot react with HCN, because they are less electrophilic than alkynes, unless we consider alkenes whose double bond is activated by electronegative groups.
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Offline victor

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Re:alkenes and aldehydes
« Reply #2 on: March 03, 2006, 06:46:36 AM »
I think alkene can react with HCN if acidic catalyst is present.
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Offline Alberto_Kravina

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Re:alkenes and aldehydes
« Reply #3 on: March 03, 2006, 07:59:17 AM »
Quote from: victor on March 03, 2006, 06:46:36 AM
I think alkene can react with HCN if acidic catalyst is present.
Yup! That's possible!
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Offline HP

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Re:alkenes and aldehydes
« Reply #4 on: March 03, 2006, 08:54:06 AM »
What about if HCN + H2O-->prussic acid :)
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Offline Alberto_Kravina

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Re:alkenes and aldehydes
« Reply #5 on: March 03, 2006, 08:58:23 AM »
Quote
What about if HCN + H2O-->prussic acid
Is this reaction possible: HCN + 2 H2O ----> HCOOH + NH3 ?
HCN is a nitrile, so it could hydrolyze to form formic acid....I don't know if this is possible, but I know that Cyanogen (CN)2 hydrolyses to Oxalic acid.
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Offline HP

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Re:alkenes and aldehydes
« Reply #6 on: March 03, 2006, 09:27:11 AM »
Yes so,  the HCN solution is unstable and decomposes on standing, giving amorphous insoluble substances, and ammonium formate, oxalic acid, &c.
I think that HCN addition to alkene(for example ethylene) could be possible in present of catalitic amount conc. H2SO4 or H3PO4(may be on solid support) because the acid sulfate or phosphate addition intermediates are very good leaving groups. Then the product HCN addition to ethylene should be acetonitrile CH3CH2CN...But i dont know such industrial process present :)
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