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The best tool I have come across so far to do this is this one: https://cactus.nci.nih.gov/osra/ I was also reading about this other one, but can't find the link to the tool itself.


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According to the Gaussian Frequently Asked Questions: In general, a stationary point is found when one of two criteria is met for a point in an optimization calculation: All four values listed in the output are smaller than the indicated thresholds. The Maximum Force and RMS Force are two orders of magnitude smaller than the thresholds shown, ...


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It is a good question, it is a gemstone hiding in the mud. I have searched the Cambridge database, all the bis-acetylacetonatonickel complexes which have four coordinate nickel centres are square planar. There are three common coordination geometries for nickel(II) which we need to consider. Tetrahedral, square plannar and octahedral. Here is a diagram (...


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Chemical formulas of the type you describe are just as valid for large molecules as for small ones. The reason they are not commonly used is that the number of possible molecules described by a given formula goes up exponentially with the number of atoms. Thus, it is much more common to describe larger molecules with more precise terms. In the case of ...


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Air, fresh water, sea water, whiskey are fluid phases, aside of solid phases. A phase is a space region of homogenous properties of matter, possibly with gradient of theses properties (like sea water profile, or solution of statically dissolved solid), with strong discontinuity of these properties at the region boundary. The gradient can be at special ...


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PubChem 3D has limits on the number of 'rotatable bonds' I recently answered a related question about PubChem 3D: Beyond the limits of MMFF94 and MMFF94s themselves, PubChem3D had several limits indicated in the accompanying manuscript: Bolton et. al. "PubChem3D: a new resource for scientists" J Cheminf. (2011) v. 3, art. 32) Not too large (with ≤...


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In hydrides that contain two or three hydrogens connected to a central atom such as $\ce{PH3}$ or $\ce{H2Se}$, the number of bonding partners does not exceed the number of available p orbitals on the central atom. In an extreme application of Bent’s rule, the most ideal bonding situation would be to have pure p-type orbitals form the required bonds and at ...


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The geometry depends on the nature of the doublets around the central atom. If the doublets are all bonding, like in $\ce{CH4},$ $\ce{SiH4}$ and $\ce{GeH4},$ the geometry of the molecule is tetrahedral, and the angles between the bonds are 109.5°. If one or two of these doublets are non-bonding, they are more cumbersome than covalent bonds. They repel the ...


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Working out the structure of a compound (organic, organometallic or organomain group) is not a simple matter. It is something which can be very intellectually taxing. I have done it many times in my life and I can tell you that for some thing you can do it in a matter of minutes while for other things it can take weeks, months or even years) The first ...


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How can an Organic chemist know the chemical formula of a natural product she isolated from an organism? There are two levels of answers. One is historical and one is modern. Historically, determining the chemical formula for had been a trivial job for most small or medium sized molecules. You do a combustion analysis, determine how much carbon dioxide, and ...


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This question cannot be answered in such a Forum. Because there is no unique answer. The method for giving a formula is a huge process. It takes hours and days and weeks to the university students and professors to be able to answer this question. Sometimes a given process is specific for a given product, and not applicable to the next substance. It is a ...


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It is because of the higher electronegativities of Br and Cl, than Hydrogen. So there is a higher repulsion of the bonding electrons.


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The larger angles can simply be explained as a result of repulsion between the larger atoms of $\ce{Br}$ and $\ce{Cl}$. Hydrogen atoms in $\ce{PH3},$ as the are so small, experience less repulsion as compared to $\ce{Br}$ atoms in $\ce{PBr3}$ or $\ce{Cl}$ atoms in $\ce{PCl3},$ therefore the larger bond angles in $\ce{PBr3}$ and $\ce{PCl3}.$


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