Orglist archive
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: ORGLIST: grignard

From: Graham Cumming <graham.cumming>
Subject: Re: ORGLIST: grignard
Date: Wed, 14 Mar 2012 09:53:06 +0000
Good suggestions on that discussion site, but I have often found
problems using the diphenylacetic acid method (with organolithiums
anyway) - if your organometallic solution is a little yellow, then it
is hard to determine the end-point.  The more vividly coloured
reagents such as phenanthrolines (I think there's one that gives a
blue end-point too, can't remember what it is) make it much easier to
spot the change.

You might also want to titrate for non-Grignard basicity (e.g. Mg
hydroxides) can be a problem in reactions.  This can be done
indirectly, by titrating for total base (simple quench and then
acid-base titration), or by using the Griganrd to do an elimination
reaction, forming MgBr2 for example, and titrating excess base
afterwards - there is a load of lit out there to be read!

Graham

On 14 March 2012 09:42, Vedran Hasimbegovic
<vedran.hasimbegovic> wrote:
> Hi there,
>
> Titration can be used, there is a forum discussion on this:
> http://www.chemicalforums.com/index.php?topic=17690.0
>
> Hope it helps
>
> //Vedran
>
>
> On Wed, Mar 14, 2012 at 3:57 AM, Shailesh kumar Pansuriya
> <shreejisky> wrote:
>>
>> Surprised by quick email. Sir. I am preparing Methyl Magnesium Iodide. 30
>> g Mg + 180 g Methyl Iodide + 500 ml Diethyl Ether and make grig.   As i need
>> the grig free from water, alcohol, aldehyde, free from unreacted Mg. but how
>> could i check the quality of grig.?
>> Really very very Thanks for reply
>>
>> On Mar 14, 2012 1:11 AM, "Guido de Silvestri" <gde>
>> wrote:
>>>
>>> Dear Shailesh....
>>>
>>> What exactly is the problem you are having with the synthesis?
>>>
>>>
>>> -----Original Message-----
>>> From: orglist-everybody
>>> [mailto:orglist-everybody] On Behalf Of Shailesh kumar
>>> Pansuriya
>>> Sent: Tuesday, March 13, 2012 3:08 AM
>>> To: OrgList
>>> Subject: ORGLIST: grignard
>>>
>>> hi, any one who help me to solve the problems in grignard synthesis?
>>>
>>>
>
>
>
> --
> What I know, I believe. -- L. Wittgenstein
>

Orglist archive
Subscribe: (hidden), Post: (hidden).