gothchemist

I am starting this thread as a place where people can leave their thoughts on the terrible explosion which occurred on the 24 March at the National College of Chemistry, Mulhouse, France. My thoughts go out the friends and family of the dead Professor and the injured students and staff. I also would like to pay my respects to the dead professor for his work in researching high risk procedures for the advancement of science. I think we all need to the remember the triumphs of science despite the risk over the years. It people like the professor that died that has enabled the human race as a whole to learn and advance. My salute to scientists in all areas, may your good work continue.

As an addition to the previous post: the molecule Pasteur separated was tartaric acid. Here is a link: http://en.wikipedia.org/wiki/Louis_Pasteur

Methods of Separation: Chiral Chromatography: Pass a solution of the racemic mixture through a column containing a chiral solid matrix (one isomer of a chiral solid) and the different enantiomers will have different elution times. Enzymatic resolution: Take for example a racemic mixture of chiral alcohol i.e 50:50 add enzyme that only oxidises one enantimer to the ketone (you then get 50% of one enantiomer of the chiral alcohol and 50% of the corresponding non chiral Ketone) and then reduce the ketone back to the alcohols using standard chemistry e.g borohydride (which will turn the 50% ketone component into a 50:50 mixture of the two enantiomers of the chiral alcohol, so you end up with a 75:25 mixture of the two alcohol enantiomers overall). If you then repeat the oxidation and reduction steps again you get a 87.5:12.5 mixture, and again 93.75:6.25. If you repeat above procedure six times you will end up with greater than 99% of the enantiomer of the chiral alcohol that isn't oxidsed by the enzyme.

While dextrorotary can be used to designate the (+)-isomer and laevorotary the (-)-isomer of a particular compound, compounds labeled D (dextro) and L (laevo) are not necessarily the + and - isomers repectively. The D and L terminology is from the early days of chemistry, in a time before X-ray crystallography when proof of configuration of a compound was carried out via degradation from a isomerically pure source typically the two isomers of glyceraldehyde with the + isomer being designated D and the - L. Unfortunately when D-glyceraldehyde is degradated to the structurally related D-lactic acid the isomer is the - one not the +. The D and L terminology are use to related molecules as being structurally related to either D or L gyceraldehyde not the direction of rotation of plain polarised light. This designation is not used today except in areas estabalished by tradition such as sugars and amino acids. Today enantiomers are designated either +/- if the configuration is unknown or R/S if it is known. A full explaination of this is found here : http://www.cem.msu.edu/~reusch/VirtualText/sterism3.htm#isom13.

Good: Acetone, Valinol (smells like bourbon biscuits), t-Butylbenzene, Cyclohexanecarbaldehydes, Diethylether, Menthols, Toluene Bad: 2,4,4-Trimethyl-2-oxazoline (smells like rancid cooking fat), Acetophenones, Halophenols, Ethylacetate, PCl3, PhPCl2, Ph2PCl, SOCl2, Acid Chlorides