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Henry Rzepa's Blog

Henry Rzepa's Blog
Chemistry with a twist
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HypervalencyBondingELFFluorineHiberty And CoKimya Bilimleriİngilizce
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In the previous post, I ruminated about how chemists set themselves targets. Thus, having settled on describing regions between two (and sometimes three) atoms as bonds , they added a property of that bond called its order . The race was then on to find molecules which exhibit the highest order between any particular pair of atoms.

HypervalencyGas PhaseMt. EverestPenceKimya Bilimleriİngilizce
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Climbers scale Mt. Everest, because its there , and chemists have their own version of this. Ever since G. N. Lewis introduced the concept of the electron-pair bond in 1916, the idea of a bond as having a formal bond-order has been seen as a useful way of thinking about molecules. The initial menagerie of single, double and triple formal bond orders (with a few half sizes) was extended in the 1960s to four, and in 2005 to five.

Interesting ChemistryChairConformational AnalysisFinal Resting EnergyFree EnergyKimya Bilimleriİngilizce
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In an earlier post, I re-visited the conformational analysis of cyclohexane by looking at the vibrations of the entirely planar form (of D 6h symmetry). The method also gave interesting results for the larger cyclo-octane ring. How about a larger leap into the unknown? Let us proceed as follows. One fun game to play in chemistry is to invoke i so-electronic substitutions.

GeneralInteresting ChemistryAdolf Von BaeyerAnimationCKimya Bilimleriİngilizce
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Like benzene, its fully saturated version cyclohexane represents an icon of organic chemistry. By 1890, the structure of planar benzene was pretty much understood, but organic chemistry was still struggling somewhat to fully embrace three rather than two dimensions. A grand-old-man of organic chemistry at the time, Adolf von Baeyer, believed that cyclohexane too was flat, and what he said went.

HypervalencyInteresting ChemistryBondQuadrupleKimya Bilimleriİngilizce
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So ingrained is the habit to think of a bond as a simple straight line connecting two atoms, that we rarely ask ourselves if they are bent, and if so, by how much (and indeed, does it matter?). Well Hursthouse, Malik, and Sales, as long ago as 1978, asked just such a question about the unlikeliest of bonds, a quadruple Cr-Cr bond, found in the compound di-μ-trimethylsilylmethyl-bis-[(tri-methylphosphine)

Chemical ITRDFSemanticKimya Bilimleriİngilizce
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A Semantic blog is one in which the system at least in part understands about (some of the) concepts and topics that are in the content. The idea is that this content can be more intelligently (is that the correct word?) and importantly, automatically searched, harvested, and connected to the same or similar concepts found elsewhere in other blogs and the Web as whole.

Chemical ITGeneric SolutionKimya Bilimleriİngilizce
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After around 40 posts here, I decided to take a look at the whole effort and ask some questions. For example Should (scientific) blogs be used to report new science, or merely opinion on existing science (see this blog also)? If the former, should they be abstracted in the manner of regular articles (e.g. by CAS etc). Unlike e.g. a journal, a blog is often (and certainly in this case) the effort of an individual.