From: Jacob Zabicky (zabicky$##$bgumail.bgu.ac.il)
Date: Fri Oct 03 2003 - 11:55:54 EDT
Dear Fergus,
If by now you haven't pocketed a couple of dozen ready-to-wear
experiments, here is a suggestion inspired on analytical methods, which
needs some development on your side.
1. The point of the synthesis is producing a diazo dye by the coupling
reaction of a a phenol with a diazonium salt.
2. Possible by-products are: a) coupling at an alternative and less
reactive site of the phenol substrate; b) partial hydrolysis of the
diazonium salt leading to formation of a phenol that is prone to
coupling with the diazonium ion; c) multiple couplings on the same
substrate; d) unreacted phenol substrate or diazonium ion reagent. At
least the main product of item 1 and the by-products of a) to c) should
give nice bands on any chromatographic column.
3. You have a choice to go all the synthetic route, which includes as
first step preparation of a diazonium salt solution from the
corresponding amine (no need to isolate the product, and IMHO cheaper
and more didactic), or buying one of the diazonium salts offered by
reagent vendors.
4. Additional didactic points: a) the importance of the order of
addition of reagent in an organic synthesis; should the phenol solution
be added to the diazonium salt solution, or viceversa; I think it
should make a considerable difference, which can be checked by part of
the students doing it otherwise. b) The development of the reaction may
be followed by TLC on small plates, which may also aid in planning the
big column.
5. The main product and the by-products should be easily distinguished
by the H and C NMR modalities.
Some references:
J. Itoh et.al, Chem. Abstr. 122, 16630 (1995)
E. N. Myshak et al, J. Anal. Chem., 52, 939 (1997)
J. S. Esteve Romero et al., Analyst, 119, 1381 (1994)
L. Alvarez-Rodriguez et al., J. AOAC Int., 82, 937 (1999)
O. Agraval and V.K.Gupta, Microchem. J.,62, 147 (1999)
S. M. El-Ashry et al., Microchim. Acta, 135, 191 (2000)
S. G. Dmitrienko et al., Chem. Anal. (Warsaw), 40, 291 (1995)
M. Battacharjee and V. K. Gupta, Chem. Anal. (Warsaw), 39, 687 (1994)
All the best,
Jacob
3. You have
On Friday, Oct 3, 2003, at 11:21 Asia/Jerusalem, Lalor, Fergus wrote:
> Fellow organikers -
> We have recently decided to remove the acetylation of ferrocene from
> our
> 3rd. Year organic practical class because of concerns about the
> toxicity of
> the major product, acetylferrocene. Hence we are now looking for a
> suitable
> replacement. The original reasons for including the ferrocene
> experiment
> were:
> (1) Hands-on experience of a transition metal organometallic compound
> which
> does not require special conditions or apparatus..
> (2) Experience of purification of ferrocene by vacuum sublimation.
> (3) Experience of a Friedel-Crafts experiment on an unusual substrate
> (4) Experience of a simple synthetic procedure where the products are
> easily
> separable by flash chromatography and, importantly, are all coloured
> and
> rtherefore eadily visible on the column.
> (5) Ready identification of major and minor products by H and C NMR.
>
> Point (1) is no longer relevant as an equally relevant experiment is
> now
> part of their inorganic practical. Point (2) is of marginal importance
> as
> sublimation is hardly a main-stream purification technique. Point (3)
> was
> always problematical as - unfortunately - the mysteries of our
> timetable
> ensure that the practical takes place a whole term ahead of the
> relevant TM
> organometallic lectures.
>
> What we need as a replacement, then, is a new experiment that fits
> criteria
> (4) and (5). I and a colleague have done some trawling through J.
> Chem. Ed.
> and some lab textbooks without finding anything really appropriate. Any
> suggestions would be most gratefully received. I should mention that
> our
> replacement should be capable of being completed in two 4 hr laboratory
> sessions.
> Regards -
> Fergus
>
>
> Dr. Fergus John Lalor
> Senior Lecturer
> Department of Chemistry
> University College
> Cork
> Ireland.
> Telephone: 00353-21-4902317
> Fax: 00353-21-4274097
> _______________________________________________
> ORGLIST - Organic Chemistry Mailing List
> Website / Archive / FAQ: http://www.orglist.net
> To post a message (TO EVERYBODY) send to everybody$##$orglist.net
> To unsubscribe, send to everybody-request$##$orglist.net the message:
> unsubscribe your_orglist_password your_address
> List coordinator: Joao Aires de Sousa (coordinator$##$orglist.net)
>
***************************************************
Prof. Jacob Zabicky
Institutes for Applied Research
Ben-Gurion University of the Negev
P. O. Box 653, Beer-Sheva, 84105, Israel
Phone: +972-8-6461271; Fax: +972-8-6472969
zabicky$##$bgumail.bgu.ac.il
http://www.bgu.ac.il/IAR/Zabicky.htm
-------------------------------------------------
Private:
P. O. Box 12366, Beer-Sheva, 84863, Israel
Phone: +972-8-6496792
_______________________________________________
ORGLIST - Organic Chemistry Mailing List
Website / Archive / FAQ: http://www.orglist.net
To post a message (TO EVERYBODY) send to everybody$##$orglist.net
To unsubscribe, send to everybody-request$##$orglist.net the message: unsubscribe your_orglist_password your_address
List coordinator: Joao Aires de Sousa (coordinator$##$orglist.net)
This archive was generated by hypermail 2.1.4 : Fri Oct 03 2003 - 12:27:02 EDT