• Home
  • About
  • Chemistry
    • Solvent of the Week
    • Compound of the Week
    • Reagent of the week
    • Publications
    • Translations
    • Glassware designs
    • Advanced Preparative Separation
    • Videos
    • A day in a mineral lab
    • A day in a wine lab
    • A day in a polyurethane lab
  • Philosophy
    • Poor Matthew
    • On Australian coins
    • On global warming
    • On aluminium cans
    • Questions to ask potential housemates
    • Why chemistry skills are now less valued than they were
    • Tribute to Mr John Clarke
    • Theory on Covid-19
  • Photos
  • Blog
MJLPHD

A carbohydrate chemistry project

5/10/2014

1 Comment

 
PictureRing opening of sucralose
At the start of my PhD, my supervisor gave me a project in which I would try to do a ring opening of sucralose using periodate to get a tetra-aldehyde product.

PictureMolecular structure of Guar gum
The idea was to optimize this process and then to transfer these same conditions to convert guar gum to its tetra-aldehyde, convert the aldehyde groups to alkynes by a Corey–Fuchs reaction and then do click chemistry (copper catalyzed azide-alkyne cycloaddition) with a variety of azides in order to functionalize guar gum.

Looking back on it now it seems a bit far fetched. I gave it a try but I eventually found my way into another project involving isocyanates and hydantoins. To begin my investigation, I carried out a solvent survey of sucralose and guar gum. The results, posted below, reminded me that carbohydrates really don't dissolve in much.
Picture
Solubility of sucralose and guar gum in selected solvents
While I didn't get any further than this, the next step would be to try blends of water with organic solvents. I would also like to try cyclohexanone.
1 Comment

Rotavaping DMF

1/10/2014

0 Comments

 
I have found that researchers in many synthesis labs are unaware that dimethylformamide (DMF) can be removed by a rotary evaporator. Providing the product compound is not heat sensitive, removal by evaporation is a much better option than a liquid/liquid workup which would waste a lot of solvent.

Picture
Dimethylformamide
Picture
A 100 mL non-reversible splash-guard
To rotavap DMF, Dow Corning high vacuum grease must be freshly applied to the joins and Keck clips used to hold the flask onto a non-reversible splash-guard.
With the water bath at 55 °C the vacuum will need to be lowered to 25 Torr; at 70 °C the required vacuum is only 25 Torr.
Picture
A 100 mL pre-weighed flask and a 500 mL non-reversible splash-guard attached to a rotary evaporator
The utility of the non-reversible splash-guard is not so much the prevention of mess or loss from bumping, rather that it reduces the distance that the DMF fumes must travel to be removed from the flask. This is because DMF vapours will quickly condense as they get further away from the flask which is in a hot water bath (55-70 °C) and come into contact with the glass parts of the rotavap that are at room temperature (~20 °C). Shortening this distance makes DMF removal from a mixture much easier.
Picture
Note the shortened distance that the DMF vapours will have to travel before condensing when using this splash-guard. It is ~4 cm less.
Removing DMF is slow and is prone to bumping so only lower the pressure gradually. You might want to leave a note for your co-workers saying that you are removing DMF and go for a cup of coffee.
0 Comments

    Matthew's Chemistry blog.

    A chronicle of tips, tricks & stories

    Contributions from readers are welcome and should be emailed to matthew.leonard742@gmail.com

    Archives

    September 2016
    December 2015
    September 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    July 2014
    May 2014
    March 2014
    February 2014
    January 2014
    December 2013
    November 2013
    October 2013

Powered by Create your own unique website with customizable templates.