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39 votes

Storing hydrofluoric acid before the invention of plastics

In the original 1771 experiment, Scheele used a very simple setup consisting of a glass retort with a glass receiver (round-bottom flask). Yes, the glass was etched to some degree by the fumes, but ...
andselisk's user avatar
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35 votes
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Which is the currently accepted mechanism of a Wittig reaction?

tl;dr: I don't think there is any mechanism that is 100% correct, and, in cases like this especially, I think it would completely depend upon what set of carbonyl/ylid/base/solvent etc. was used. But, ...
NotEvans.'s user avatar
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21 votes
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Theoretical basis behind orbital correlation diagram for pericyclic reactions

Introduction Instead of the usual cycloadditions (which has some extra complications in terms of the reacting orbitals), let's consider the concerted reaction $\ce{H2 + D2 -> 2HD}$. We'll come ...
orthocresol's user avatar
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21 votes
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How can benzaldehyde have a pKa of 14.9?

Significant amount of geminal diol of benzaldehyde exists in an aqueous solution of benzaldehyde at 25 °C because $\mathrm{p}K_{\text{hyd}} = 2$ (Ref. 1) The $\mathrm{p}K_{\mathrm a}$ of benzyl ...
Mathew Mahindaratne's user avatar
20 votes
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Melting point of aspirin, contradicting sources

Wolfram company doesn't conduct any experimental determinations of physical constants for chemical compounds and uses literature data sources. The webpage for ChemicalData Source Information lists ...
andselisk's user avatar
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18 votes

Do symmetric hydrogen bonds in neutral molecules exist?

This question crossed my mind during a lab today because we were making $\ce{Ni(dmg)2}$, which is shown below. Well first, this is charged in some sense, but it is net-neutral. Also, the ...
jheindel's user avatar
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18 votes

Do symmetric hydrogen bonds in neutral molecules exist?

It appears that, perhaps, water may have symmetric hydrogen bonds between oxygen atoms, but it would take at least 60 GPa of pressure, to make water to bond like that. I guess water stops being ...
Mithoron's user avatar
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18 votes

What is the least dense liquid under normal conditions?

Isopentane $\ce{C5H12}$ has the density of $0.6201~\mathrm{g\,cm^{-3}}$ at $20~\mathrm{^\circ C}$ [1, p. 3-330]. References Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and ...
andselisk's user avatar
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18 votes
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Does the largest known cycloalkane contain 288 carbon atoms?

According to Makromol. Chem., Rapid Commun. 1985, 6 (3), 203–208[1], Kwang Sup Lee and Gerhard Wegner, attempting the synthesis and study of $n>100$, $\ce{C_nH_{2n}}$ cyclo-alkanes and linear ...
Safdar Faisal's user avatar
17 votes

Is Hexafluorocyclohexane the "Most Polar" Small Molecule?

At first I checked common organic compounds and solvents in CRC Handbook [1, 9-59] that have dipole moment above $\pu{4.5 D}$: \begin{array}{llrr} \hline \text{Name} & \text{Formula} & \text{...
andselisk's user avatar
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16 votes
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Storing hydrofluoric acid before the invention of plastics

Based on research inspired by andselisk's answer, chemists stored it in glass vessels coated in wax (similar to the receiver setup Scheele used to prove the silicon dioxide precipitate was from the ...
Doktor J's user avatar
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16 votes
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Caffeine molecule representation and orientation

Wondering if there are IUPAC rules or conventions about structure orientation. There are recommendations, which aren't really rules per se (in fact even the IUPAC nomenclature books are all ...
orthocresol's user avatar
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15 votes
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What is "super" in superphosphate?

The term superphosphate is really old, even well before the concept of atoms was proposed by Dalton. Therefore it is difficult to rationalize the choice of this terminology. In the unabridged version ...
ACR's user avatar
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14 votes
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What is "gold number"?

A red gold sol is a colloidal suspension of gold nanoparticles with average size of particles less than 100 nm. The suspension is quite stable — the nanoparticles don't aggregate because of the ...
vapid's user avatar
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14 votes
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What are introductory level books on chemical engineering?

I'm studying chemical engineering for more than two years and what I can tell you is that there is not really a lot of "good" books you may read as an introduction. You have to understand ...
ParaH2's user avatar
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14 votes

Density range of table salt?

The density of $\pu{2.17 g/cm³}$ refers to the density within a crystal of NaCl. In chemical engineering, the terms of powder density, tapped powder density and settled apparent density take into ...
Buttonwood's user avatar
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13 votes
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Is there an iron–iron bond in diiron nonacarbonyl?

tl;dr: There probably isn’t an Fe–Fe bond. We should probably stop drawing an Fe-Fe bond. Textbooks and lecturers should really stop teaching students that there is an Fe-Fe bond. But all that said, ...
NotEvans.'s user avatar
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12 votes

List of functional groups in a molecule

Norbert Haider from the University of Vienna has been working on the identification of functional groups for quite a while. You might want to have a look at his checkmol/matchmol tool, which natively ...
Klaus-Dieter Warzecha's user avatar
12 votes

What is "chemical pressure"?

External and internal pressure To study the effect of pressure on properties of a solid, is equivalently to learn how changes in volume transform physical parameters. For external pressure at ...
Linear Christmas's user avatar
12 votes
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Image of crystal structure

I recommend to fetch the crystal structures of inorganic compounds via specific Google search pattern site:crystallography.net <keyword(s)>, e.g. in your case ...
andselisk's user avatar
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12 votes
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Inorganic chemistry handbook with reaction lists

An Intro in Russian edition of Reactivity of Inorganic Substances by Lidin et al. claims its uniqueness: Настоящее пособие носит информационно-справочный характер, не имеет аналогов в отечественной и ...
andselisk's user avatar
  • 38.3k
12 votes

What is the least dense liquid under normal conditions?

According to Hans Jaffe: Eine metallische Verbindung von Lithium mit Ammoniak. Elektrische Leitfähigkeit und galvanomagnetische Effekte. Z. Physik 93, 741–761 (1935) https://doi.org/10.1007/...
Karl's user avatar
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12 votes

What is "super" in superphosphate?

Superphosphate is a name used in agriculture, therefore, it does not mean the same super in the superoxides. There are two important types of fertilizers in agriculture: Nitrogenous and phosphatic ...
Mathew Mahindaratne's user avatar
12 votes
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Does high pressure reverse reaction between zinc and sulfuric acid?

As a very rough estimation of pressure when the hydrogen redox potential equals zinc standard redox potential, we can use the extrapolation of the Nernst equation: \begin{align} E^\circ_\ce{Zn/Zn^2+} &...
Poutnik's user avatar
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11 votes

Do symmetric hydrogen bonds in neutral molecules exist?

In Schaefer's paper,[1] which you linked, the authors describe nitromalonamide as being the compound with the lowest calculated barrier to intramolecular proton transfer, or tautomerisation. Earlier ...
orthocresol's user avatar
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11 votes

Is Hexafluorocyclohexane the "Most Polar" Small Molecule?

Calicene ($4.66~\pu{D}$, 14 atoms) and its derivatives are also good candidates. For Hexaphenylcalicene, a hydrocarbon with 74 atoms, a dipole moment of $6.3~\pu{D}$ has been reported.[1] 2,3-dicyano-...
aventurin's user avatar
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11 votes

Do modern dispersion-corrected DFT methods give more accurate molecular geometries?

I am afraid I do not know of a paper specifically discussing the effects of DFT dispersion corrections on intramolecular properties. However, it should be noted that for short-range descriptors (such ...
F'x's user avatar
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11 votes
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Modern open-source tools for simulation of NMR spectra

In Org Biomol Chem 2016, 14, 3943, Goodman reports the replacement of some "tradition" (expensive) programs with free/open-source ones, as applied to their dp4 method. Specifically: Molecular ...
NotEvans.'s user avatar
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11 votes
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Radius of hydride (H⁻) ion

Unfortunately, there is no caliper-like tool to measure ionic radii directly. They are determined based on experimental data such as crystal structure or crystal lattice energy using empirical ...
andselisk's user avatar
  • 38.3k
10 votes
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What is the structure of trifluoromethanesulfonic acid in the gas phase?

Has the structure of trifluoromethanesulfonic acid or a structurally strongly related acid been studied in the gas phase? (Please provide a reference) Yes. See Gas Phase Structure of Methyl ...
DavePhD's user avatar
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