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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: sharbeldam on May 01, 2021, 06:37:37 AM

Title: Can PCl5 be used to test between alcohol and ketone/aldehyde?
Post by: sharbeldam on May 01, 2021, 06:37:37 AM

It reacts with alcohols and it also reacts with ketone to give geminal dihalide, but can someone go deeper into the reaction with ketone? does it release gas or change color? can PCl5 be used to test for ketones? id be really happy for detailed answer

Title: Re: Can PCl5 be used to test between alcohol and ketone/aldehyde?
Post by: rolnor on May 01, 2021, 08:58:32 AM

I would say no. Its better with IR or NMR.

Title: Re: Can PCl5 be used to test between alcohol and ketone/aldehyde?
Post by: billnotgatez on May 02, 2021, 10:53:28 AM

Quote from: rolnor on May 01, 2021, 08:58:32 AM

I would say no. Its better with IR or NMR.

@rolnor
just curious
What do you think could be done without the nice machines

Title: Re: Can PCl5 be used to test between alcohol and ketone/aldehyde?
Post by: rolnor on May 02, 2021, 12:15:19 PM

You can use 2,4-dinitrophenylhydrazine as test for ketones and aldehydes, it shows yellow-orange spots on TLC.

Title: Re: Can PCl5 be used to test between alcohol and ketone/aldehyde?
Post by: Meter on May 02, 2021, 03:08:21 PM

Quote from: rolnor on May 02, 2021, 12:15:19 PM

You can use 2,4-dinitrophenylhydrazine as test for ketones and aldehydes, it shows yellow-orange spots on TLC.

I remember doing this as one of my first organic labs. Then Tollens test was used to distinguish between aldehydes and ketones.

Title: Re: Can PCl5 be used to test between alcohol and ketone/aldehyde?
Post by: rolnor on May 02, 2021, 03:59:20 PM

Also Shiffś reagent is selective for aldehydes;
https://en.wikipedia.org/wiki/Schiff_test