nuclear chemistry

ACS Day 4: New Uranium (VI) Chemistry (non uranyl)

Hayton, from Santa Barabara, presented his recent work with uranium (VI) compounds. The chemistry of Uranium (VI) is dominated by the formation of Uranyl (UO2)2+. However, the Hayton group was able to synthesize and fully characterize U(OtBu)6 (1). The compound was reacted with aryl-alcohols in the hope of producing U(OAr)6 (2) compounds, shown below.

Unfortunately, due to the presence of lithium from earlier steps he prepared (3) and after doing a better job ridding his reagents of lithium produced (4).

The work highlights the difficulty in synthesizing stable uranium (VI) compounds, but perhaps if they didn’t use the electron withdrawing fluorine groups with their arylalcohols they might better stabilize the U+6.

More Info: Synthesis and Characterization of Three Homoleptic Alkoxides of Uranium…

Mitch

By August 21, 2008 1 comment nuclear chemistry, synthetic chemistry

ACS Day1: New Actinide Solvent Extractors

The ability to selectively extract actinides out of nuclear waste remains a hot research topic. Today Hancock, from Wilmington, gave a presentation on several tetradentate ligands that bind to actinides more strongly than other smaller metals. The systems he investigated are shown below.

The PDA system was highlighted for its rigidity, fluorescent potential, and the size of its cavity. Some formation data below.

These types of systems look promising and are a nice upgrade over traditional old-school extractors like tributylphosphate(TBP).

Much of the talk was covered in this recent paper: Affinity of the Highly Preorganized Ligand PDA…

Update 1: A Chemical Sabbatical linked here: Hooray! Aqueous Transition Metal Chemistry Talks

Mitch

By August 17, 2008 1 comment nuclear chemistry

ACS Endorses Quackery

I’ll be attending the ACS-Philadelphia conference next week. One of the sessions sponsored by the Environmental division is called “New Energy Technology” on Wednesday morning out at the DoubleTree-Maestro B. The title implies itself to wonderful talks discussing frontiers in applied energy chemistry. Unfortunately, the session is completely dominated by the left-field cold fusion people. A list of the talks are shown below

  • Cold fusion in light of green chemistry (Jan Marwan)
  • Low energy nuclear reactions research: 2008 update (Steven B. Krivit)
  • Overview of LENR research: Critical steps on the pathway to technology(Michael Charles Harold McKubre)
  • Macroscopic quantum dynamics and the problems of loading in Pd-H(D) systems (Antonella De Ninno, Emilio Del Giudice, Antonio Frattolillo)
  • CR-39 studies of Pd/D codeposition (P. A. Mosier-Boss, Stanislaw Szpak, Frank E. Gordon, Lawrence Forsley)
  • Study of the nanostructured palladium deuterium system (Jan Marwan)
  • Sonofusion from deuterons to helium (Roger Stringham)

My feelings on cold fusion research have been stated previously here: The difference between cold fusion and cold fusion

It would be in good taste to attend the session, and let them have the opportunity to present their research, but I question whether I could sit through it. If you find yourself bored on Wednesday morning and ready for a lively debate, I’d recommend attending this session.

P.S. Expect dispatches from the conference. I’ll be covering a wide slice of the sessions with my new ACS press-pass: ACS-2008 Philadelphia.

Mitch

By August 12, 2008 8 comments nuclear chemistry

Addressing Marinov’s Element 122 Claim

Note 1: It is an unfortunate consequence of the internet age to be forced to address public misconceptions of research that is published by press-release rather than peer-review. Society & science are not served well from the absence of even cursory peer-review. It should be noted that some of the authors in the paper have a colorful past, but the critique below will be on evidence provided within the manuscript the authors have submitted.

In Marinov’s element 122 paper, Evidence for a long-lived superheavy nucleus.., a fantastical claim is made for the identification of element 122 with standard thorium samples. It should be strenuously noted that element identification (id est determination of the number of protons, atomic number (Z)) can not be definitively determined by mass spectrometry when the exact mass of the element is not known. Yes, there are many models that can extrapolate what the mass of an unknown isotope should be, but overly broad best guessing is not the way science in conducted.

The paper infers a mass accuracy for their mass spectrometer of 0.040 amu and this error will be used to determine the validity of their data. The first figure showing evidence of element 122 is shown below.


The figure shows their data from summing the thorium sample 5 times from their 1st run.

As the figure is lacking a significantly intense peak near 292.010 amu corresponding to 238U40Ar14N+ that is seen in later runs, I would be forced to chalk those signals to inherent noise in the instrument, especially as no blank spectrum was provided as reference for this data series.

The figure shows their data from summing the thorium sample 60 times from their 2nd run. Top spectra is sample, bottom spectra is of the blank.

The peaks from 238U40Ar14N+, mentioned earlier, can be clearly seen in this spectrum. The authors fail to scale the blank’s intensity (y-axis) to the same level as the sample which makes comparisons unnecessarily difficult. The blank’s intensity axis is larger than that of the samples, which is very unusual as one tends to have to zoom into a blank rather than zoom out to make a scientific point. I am also confused as to what the peaks labeled x1/5 mean (was data altered to scale these peaks down?), I do not know. As the x1/5 peaks in the blank are not seen in their thorium sample, one has to wonder why this is so. Has the detection limit already been reached?


The figure shows their data from summing the thorium sample 200 times from their 3rd run. Top spectra is sample, bottom spectra is of the blank.

This data set has the largest statistics as it is a sum of 200 spectra. The blank in this figure has obvious peaks near 292.230 and 292.280 amu. The blank peak at 292.230 is also seen in the sample spectrum, and is now a dominant peak in that spectrum. Any good data set should be at least 3 times the peak height of blank noise, when the signals are so close together, but this is not the case in this figure. Even if referencing the 2nd blank peak at 292.280, the signals attributed to element 122 are at best 2-2.5 times blank background peaks.

The claim that there was no molecular ion formation from hydrocarbon presence from their vacuum pump is also not realistic. From the sensitivities claimed in the paper the presence of pump oil should of been detected.

The authors give several theoretical hypotheses why element 122 should be stable, but these claims will not be evaluated as I see no convincing evidence of the identification of element 122.

Note 2: Link to paper: Evidence for a long-lived superheavy nucleus with atomic mass number A=292 and atomic number Z=~122 in natural Th
Note 3: First coverage of claim was from The Physics ArXiv Blog: First superheavy element found in nature

Mitch

Note 4: Mitch is a nuclear chemistry PhD student at UC Berkeley studying the chemistry and physics of elements above Lawrencium (Z>103) in the Heavy Element and Actinide Chemistry group.

By April 29, 2008 17 comments nuclear chemistry