musings on music and life

October 31, 2012

Backtracking through the literature – fluorine in nature?

Filed under: Chemistry — Tags: — sankirnam @ 5:57 pm

I have been very busy lately, which is why the posts have been so sparse. What with election fever (CLEARLY ROMNEY IS THE ONLY MAN WHO CAN SAVE AMERIKA!!!) and my co-PI’s (Prof George Olah) 85th birthday earlier this month, things have been very busy around here.

This paper from Angewandte Chemie has been on the top of my pile for a while. It discusses the occurence of free, elemental fluorine in nature. Fluorine, as I have discussed before, is probably the most chemically reactive element on the periodic table. Compounds of fluorine with other atoms are usually exceedingly stable, and fluorine, when compared with other elements, usually forms the strongest single bonds with other elements. Thus, it was thought for a long time that fluorine could not exist in its free form in nature due to its reactivity. Indeed, almost all of the fluorine found in nature exists in fluorspar (calcium fluoride).

What intrigues me about this paper is two things. One, this paper demonstrates the existence of fluorine in nature before the existence of free chlorine or bromine! If one were to make a case for potentially the most reactive element existing free in nature, it would make sense to have some precedent (such as the existence of Cl2 or Br2 in nature). To the best of my knowledge, chlorine or bromine have not been observed in their elemental forms in nature.

I am not calling the capabilities, knowledge, or experimental methods of the authors into question – this is simply a critical view of the publication. The second thing that intrigues me about the paper is a statement made by the authors: “We compared the smell of crushed “antozonite” directly with authentic F2 gas and unambiguously confirmed that the odor of the mineral corresponds to F2. The smell of F2 is decisively different from that of O3, Cl2, HOF, HF, OF2, and XeF2, which were also smelled in direct comparison”. Now, I consider myself a reasonably courageous and brave man, but these guys definitely take the cake for having balls of steel. I don’t think I can be convinced to directly smell any of the above compounds (and definitely not HF or F2), and I don’t think my respiratory tract would be the same afterwards. Anyway, take from this what you will.

Advertisements

October 28, 2012

Another plug…

Filed under: Carnatic Music — sankirnam @ 9:04 am

Another plug...

October 15, 2012

Amazing tabla solo

Filed under: Uncategorized — Tags: — sankirnam @ 12:49 pm

I have never heard of Pandit Samar Saha until now, but… wow. Just look at his amazing dexterity and control over the instrument. I hope to be able to achieve this one day on the mrudangam, but it will take decades of practice from where I am now. This video speaks for itself.

October 12, 2012

On the Nobel Prize in Chemistry 2012

Filed under: Chemistry — Tags: — sankirnam @ 9:48 am

It was announced on Wednesday that the Nobel Prize in Chemistry for 2012 has been awarded to Robert J. Lefkowitz and Brian K. Kobilka “for studies of G-protein-coupled receptors”. While I am not doubting the significance of this award or the relevance of this topic towards advancing the state of mankind, it is debatable as to whether this should actually be considered a chemistry topic. A lot of prizes lately have been given to biologists under the Chemistry umbrella – as Paul (from Chembark) states, these two gentlemen may not even consider themselves chemists (and may not even be members of the ACS!). This, in my opinion, results in the contribution of chemists to promoting the general state of humanity being overlooked. Chemjobber shares my sentiments, but Derek Lowe has a more optimistic view. It’s worth reading all of these to get a balanced viewpoint on where the future of chemistry may be headed.

So my predictions were wrong, after all. I have to wait another year for the contributions of Djerassi, Matyjaszewski, or A. J. Arduengo to be recognized.

October 7, 2012

Conference in memory of Saul Winstein

Filed under: Chemistry — sankirnam @ 9:55 am

I had alluded to Saul Winstein in a previous post on George Olah. He was one of the most eminent physical organic chemists of his day and laid the foundation of today’s detailed knowledge of carbocations through meticulous solvolytic studies. Although he never won the Nobel Prize, his memory is kept alive at UCLA through the current faculty, his family, and the various students and postdocs from around the world who worked with him. It was in this spirit that UCLA organized a day-long symposium yesterday in Winstein’s honor featuring talks by young junior faculty and senior professors who had memories of being associated with him.

Image

Dean Tantillo (UC Davis) gave a fantastic talk in the morning on carbocation rearrangements in nature, in the context of polyterpene and sesquiterpene rearrangements. He spoke in detail about the occurence of nonclassical carbocations as intermediates on the reaction coordinate of these rearrangements, and went into detail on methylcyclobutyl cations and how those may equilibrate between the non-classical and classical structures. He also spoke briefly on the intermediacy of norbornyl cations, since this was a Winstein symposium, after all.

ImageMaurice Brookhart (UNC Chapel Hill) next gave a talk on alkane-transition metal complexes. I’m not too familiar with the specifics of his work – it seems like he also did a lot of work on C-H sigma bond activation of alkanes, but I’m not sure if his work preceded that of Bergman and Shilov. He specifically mentioned a phenyldiphosphinyl iridium complex as being able to do reversible C-H activation of methane, and spoke about how the addition of t-butyl groups to the phosphines improved the ability of the iridium atom to oxidatively add to the methane C-H bonds. Could this be a precursor to Buchwald’s studies on superbulky phosphine ligands for enhancing rates of oxidative addition and reductive elimination on Pd? Who knows. The photo above is from his presentation – it is H. C. Brown and Saul Winstein at the Chicago ACS meeting, 1963. A rare photo of the two giants (and rivals!) in physical organic chemistry. I apologize for the poor image quality, as this was taken with my cellphone camera.

Image

Reuben Rieke (most people know him for his active “Rieke” metals) gave a talk immediately after the lunch break. While he is very well known for all his work on making highly active metal powders (such as “Rieke Mg” for Grignard reactions), what is less known is that he was a postdoc with Saul Winstein for a year. He talked about the work that led him to the accidental discovery of Rieke Mg, and the kinds of “impossible Grignards” that can be prepared with it.

ImageThe final session was by far the most enjoyable of the day. Jeffrey Seeman (pictured here) entertained everyone with a detailed talk down memory lane featuring rare letters of correspondence between Jack Roberts, H. C. Brown, Saul Winstein, and Paul Schleyer. He started off by showing his rare photo of Woodward standing on two guys at the beach (I don’t know who they are, unfortunately EDIT: my boss informs me that they are Prelog and Djerassi! Holy S***!!!), and showed some letters of correspondence between Jack Roberts and Woodward’s secretary, in which Jack was lamenting the fact that he could not schedule an audience with Woodward! Such was the man’s stature back then. While the norbornyl ion controversy was raging on, all these eminent chemists were corresponding regularly, and Seeman gave us a “behind the scenes” look at what was going on back in those days.

ImageJack Roberts was probably the oldest member at the symposium (at 93, if I am correct), and gave a heartfelt recollection of his association with Saul Winstein, both as his student, and later as a colleague. One of the most interesting things he shared was correspondence between him and Winstein apologizing for “stepping on Winstein’s turf” by also studying the 2-norbornyl cation solvolytically. Winstein, ever the gentleman, agreed to settle this amicably, and both came to a friendly agreement as to how they would divide up the work and publish their results! This would be completely unheard of today, with today’s cutthroat competition.

ImagePaul Schleyer (whom I finally got to see in the flesh after reading so much about him) talked about his theoretical work, with special emphasis on the NICS effect. The NICS effect is a tool that can determine if a molecule is aromatic or not based on calculated ring currents. Schleyer showed how this can also be applied as a probe for determining the amount of delocalization or non-classical character in a carbocation. Paul Schleyer sat down after his talk, only to…

ImageYes, that’s him taking a video of….

Image

the man of the hour, George Olah! Olah talked about his association with Winstein, and was especially grateful for “his friendship to a relatively unknown Hungarian chemist working in industry without the same academic pedigree as some of the people in the audience here”. Olah was most famous for his involvement in the norbornyl ion controversy, and after the passing away of Saul Winstein, the scepter of non-classical cations had been informally passed to him. Olah also recounted an incident at the Brookhaven National Organic Mechanisms conference in 1962, where he had first announced his observation of the t-butyl cation as a persistent species in antimony pentafluoride-sulfur dioxide solution. Both Winstein and H. C. Brown were there, and both men pulled him aside and warned him that “a young man should be exceedingly careful with making such extravagant claims”. Nonetheless, in case he happened to be correct, both men advised him to apply his technique to the 2-norbornyl cation and, in the case of Winstein, prove it is nonclassical, or in the case of Brown, prove it is classical.

Overall, this was a wonderful day and it was a great experience to be able to hear eminent chemists recounting the days in the “golden era of chemistry”.

Blog at WordPress.com.