IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: qooqo111 on December 18, 2010, 06:50:28 am

Title: CHEM unit 4 edexcel
Post by: qooqo111 on December 18, 2010, 06:50:28 am

this is about the reaction of aldehyde with HCN ..... so... why should the PH of the reaction be maintained or buffered between 6-8 ??
Thank You :)

Title: Re: CHEM unit 4 edexcel
Post by: Deadly_king on December 21, 2010, 10:48:21 am

Quote from: qooqo111 on December 18, 2010, 06:50:28 am

this is about the reaction of aldehyde with HCN ..... so... why should the PH of the reaction be maintained or buffered between 6-8 ??
Thank You :)

Too much of H⁺, that is at a lower pH may cause the aldehyde to get oxidised to a carboxylic acid. This is why we need to keep the aldehyde in a nearly neutral medium. ;)

If the pH is too high, the OH^- will react with H⁺ from HCN such that no reaction will take place with the aldehyde which might as well be reduced by the huge amount of OH^-.

Hope it helps :D