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9 votes
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230 views

Quenching rates in nucleation MD simulations

I am trying to perform nucleation simulations with molecular dynamics. To prepare the metastable fluid, I am equilibrating at temperatures about 30 K above the melting temperature, and then "quenching"...
9 votes
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704 views

Free Web-Based Orbital Solver to look into the Walsh orbitals of a perturbed cyclopropane

There exists a free online orbital calculator. When I draw cyclopropane it plots three molecular orbitals, but unfortunately it doesn't use the Walsh orbitals. Are there any free online tools which ...
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9 votes
0 answers
190 views

How to get defect-energy level diagram from PL data

I am reading this article Phys. Chem. Chem. Phys. , 2011, 13, 14902-14905 and seen that the authors have drawn a image of defect level using PL data Can you explain me how this diagram can be drawn ...
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9 votes
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482 views

multielectron spin-orbit coupling and energy level

For multi-electron atoms for which the Hamiltonian (including the spin-orbit coupling) reads $$H=\sum_i T_i-Z\sum_i V_i+\sum_i V_i^{\text{s.o.}}+\sum_{i>j}V_{ij}$$ The $T_i$ are the kinetic ...
9 votes
1 answer
3k views

Why does iron have an abnormally high ionization energy?

Along a period the ionization energy should increase because the atomic number is increasing, but there is negligible increase in shielding. However, $\mathrm{IE}_\ce{Mn} < \mathrm{IE}_\ce{Fe} > ...
9 votes
1 answer
219 views

The Krieger-Li-Iafrate Approximation

I am having trouble understanding what KLI approximation is. Could someone explain it to me in an intuitive/simple way?
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9 votes
1 answer
105 views

Will the sulfur-iodine cycle and Haber Method work at lower pressures and temperatures?

I have a year-long research project next year in my senior year of high school, in which we have to make some product or prototype to solve some issue. My interest was in the Liquid Fluoride ...
8 votes
0 answers
183 views

Why is octaoxygen diamagnetic?

I tried considering that according to LCAO-MO theory $\ce{O2}$ is paramagnetic, which is confirmed by experimental evidence. Since octaoxygen has the crystal structure in figure, I thought there is a ...
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8 votes
1 answer
243 views

Comparing acidic strength of crotonic and isocrotonic acids

Compare acidic strength of crotonic acid (1) and isocrotonic acid (2): On comparing $\mathrm{p}K_\mathrm{a}$ values, cis-form $(4.44)$ turns out to be more acidic than the trans-form $(4.69)$. Most ...
  • 185
8 votes
1 answer
426 views

Q-TOF vs Q-orbitrap MS data

I recently had the opportunity to analyze the same (intact protein) sample on an Agilent QTOF and a Thermo Q-Exactive, and noticed that in addition to having a moderately higher resolution the ...
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8 votes
1 answer
277 views

Experimental evidence for anomalous electronic configurations of chromium and copper

Chromium ($\mathrm{3d^5\,4s^1}$) and copper ($\mathrm{3d^{10}\,4s^1}$) are fairly well-known exceptions to the aufbau principle, often attributed to the stability of the half- or fully-filled 3d ...
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8 votes
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99 views

Alcohol to Ketone by CrO3 in cyclohexane

I have encountered an exercise question on conformation of cyclohexane and there is a statement saying, 'converting alcohol to ketone by CrO3 is much faster when R-OH is in axial position'. I would ...
  • 345
8 votes
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193 views

Comparison of C=O bond strength in metal carbonyls

Find the weakest $\ce{C=O}$ bond among $\ce{[Mn(CO)6]+},$ $\ce{Fe[(CO)5]},$ $\ce{[Cr(CO)6]}$ and $\ce{[V(CO)6]-}.$ I thought the $\ce{C=O}$ bond strength would be lowest in $\ce{[V(CO)6]-}$ since the ...
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8 votes
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68 views

Mechanism of Hypervalent Iodine Phenolic Coupling

I need some help understanding the hypervalent iodine phenolic coupling reaction taking place in this synthesis of morphine, the reaction uses $\ce{PhI(OAc)2}$ as the hypervalent reagent and ...
8 votes
1 answer
783 views

Will CO2 bubbles ever fully dissolve in water?

Background: Many aquarists keep freshwater planted tanks add $\ce{CO2}$ from a pressurized canister to their aquaria to promote plant growth. The injection is at a slow rate to get dissolved $\ce{CO2}$...
8 votes
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2k views

Does heating potato starch destroy its resistant starch?

Resistant starch, as found in potato starch, is supposed to have health benefits. There are differing opinions on whether or not heating potato starch destroys the resistant starch in it and thereby ...
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8 votes
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284 views

Why does a sealed plastic bag of dish soap, water and air expand when shaken?

I've noticed that when I put dish soap, water and a little air into a sealed plastic bag, and then shake the mixture, it forms soap suds and the bag expands significantly in volume. Why does it expand?...
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8 votes
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2k views

What are the limitations of the Born-Lande' equation?

The Born-Lande' equation is used to theoretically calculate the lattice energy, $\Delta U$, of ionic compounds. It is often cited as such in literature, $$\Delta U = -\frac{k_Az_1z_2Me^2}{4 \pi \...
8 votes
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283 views

DIY hand sanitiser solution forms spongy substance

I am trying to make my own hand sanitiser since it’s sold out everywhere. The formula I use is 1 part aloe vera gel in 2 parts 100% isopropyl alcohol. The problem is when mixing the two, the solution ...
8 votes
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113 views

Are primitive GTOs normalised before contraction, or is the resultant basis function normalised afterwards?

I'm quite curious about this: In a basis set (I'll just use minimal-basis STO-nG basis sets for convenience), the basis functions are written as a linear combination of primitive GTOs. Are the GTOs ...
8 votes
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189 views

Does water really have strong EM absorption at 3 kHz in solid and 2 GHz in liquid? Why the huge shift?

While writing this answer to the question Transmitter receiver coil separation for Electromagnetic Terrain Conductivity Measurement I ran across this large PDF file of a book Soil and Environmental ...
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8 votes
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Role of pH in azo C-coupling reaction, continued

In the question, "What is the role of pH in azo coupling reaction of diazonium with phenol and aniline?" asked by @DhrubaBanerjee and answered by @Klaus-DieterWarzecha, I find several ends ...
8 votes
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Effect of spontaneous transmutation of atom in crystal

What happens to a compound when one of its atoms changes via spontaneous nuclear reaction to an atom with very different bonding? For example, beryllium-7 turns into lithium-7 with a half-life of 53 ...
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8 votes
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1k views

Why does reduction using sodium borohydride require a protic solvent?

Recently, I was looking at the chapter on chemoselectivity in Clayden et al.'s Organic Chemistry (2nd ed.). On p. 530, it is mentioned that sodium borohydride reduction only occurs in protic solvents ...
8 votes
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3k views

Is hydronium an electrophile, nucleophile, both or neither?

Is hydronium an electrophile or a nucleophile? I expected $\ce{H3O+}$ to be a nucleophile due to the presence of electrons in the $\ce{2p}$ orbitals of $\ce{O}$. But the answer key of the test states ...
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8 votes
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470 views

Bond orders in the 3c-4e bond and 3c-2e bond

According to D. P. M. Mingos, in his book Essential Trends in Inorganic Chemistry, the bond order of the three-centre four-electron bond is approximately 0.717, which is one divided by the square root ...
8 votes
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619 views

Why are lithium (Z)-enolates more stereoselective than (E)-enolates in aldol reactions?

In aldol reactions, it is apparently a general rule of thumb that (Z)-enolates give higher stereoselectivity (for the syn aldol product) than (E)-enolates do for the anti product. Quoting Carey & ...
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8 votes
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What is the fabric in heating mantles made of?

An ordinary lab heating mantle often has a white fabric coating for the flask compartment, which looks like an inorganic fiber: Image source I'm pretty sure that for some time in the past ...
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8 votes
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812 views

Chemical bonding with f orbitals

For the elements such as rhenium, osmium, iridium how probable is for electrons in the inner 4f orbitals to gain energy and take part in a molecular orbital (such as an $f^2 d^2 s p^3$ hybrid orbital) ...
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472 views

Sulfonyl azides: diazo or azide transfer?

Sulfonyl azides, $\ce{RSO2N3}$, are capable of acting as sources of electrophilic azide ("$\ce{N+3}$"), but are also capable of effecting diazo transfer, as shown in the scheme below, taken from ref 1:...
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8 votes
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222 views

IUPAC names accidentally differing in hyphen only

Here is an example of two compounds $$\ce{CH3CH2COOCH3}$$ vs $$\ce{(CH3)2CHCOO-}$$ i.e. vs whose possible IUPAC names methyl propanoate vs methylpropanoate accidentally ...
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8 votes
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Nomenclature: equivalent atoms by single locant

Sometimes the IUPAC name is too verbose despite the structure's high symmetry. If we could use only the first locant of the ("topologically symmetrically") equivalent set of locants, and designate all ...
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8 votes
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Where is bifurcation situated on cyclohexane isomerisation PES?

I am wondering what does PES for cyclohexane isomerisation looks like. I have two possibilities in mind but each has some kind of vagueness. 1) Starting from boat conformation minimum, followed by ...
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8 votes
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356 views

Why do chlorinated silanes have lower boiling points than their methane analogs?

The boiling points of the chlorinated silanes and methanes are given below: $$\begin{array}{ccc} \hline \text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
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8 votes
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Tables/database/literature of specific or optical rotation

I'm looking for a comprehensive reference of experimental specific rotation or optical rotation data. It can be a published literature review, a free web database with API access or one that permits ...
8 votes
0 answers
94 views

Stereoselectivity of 1,3-dipolar cycloadditions

How do the 1,3-dipolar cycloadditions follow the endo rule as in the reaction below, where the anti diastereoisomer is formed predominantly?
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8 votes
0 answers
215 views

New finding in cobalt compound that absorbs oxygen - is it really a breakthrough?

Very recently Chemical Sciences published results of the discovery of a new cobalt compound that can absorb oxygen at presumably a higher capacity than what has been achievable before. The paper is ...
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Identifying Alkyl Ligands as Pi Donors or Pi Acceptors in Transition Metal Complexes

Just wondering if there was a systematic way to identify an alkyl ligand as a $\pi$ acceptor or $\pi$ donor in a transition metal complex? Although various sources indicate that weak field ligands ...
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366 views

Grubbs, Wittig & hydroboration reactions and Woodward-Hoffmann rules

Several organic mechanisms I know involve [2+2] cycloadditions and retro-[2+2] cycloadditions, namely: The Wittig reaction Hydroboration of an alkene Olefin metathesis (using Grubbs' catalyst) How ...
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7 votes
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Mathematical models of oscillatory chemical reactions

I am a mathematician working on real-life models in ordinary differential equations. I want to know if there are any models of oscillatory chemical reactions that consist of three ordinary ...
7 votes
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156 views

Why do poisoned catalysts (Lindlar, nickel borate) result in partial hydrogenation of alkynes?

I read that alkene is more reactive than alkyne, so in hydrogenation of alkynes, it's difficult to isolate the alkenes. But with poisoned catalysts like Lindlar's catalyst or Nickel-Boron (Ni2B), they ...
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Changing the level of theory for organometallic compounds

I'm finishing my Ph.D. in Inorganic Chemistry and having a debate with my supervisor. The work in question have two organometallic compounds A and B. The structures are based on X-Ray Diffraction, so ...
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Is a hydrocarbon bio-battery feasible?

Hydrocarbons have some of the highest energy densities and specific energies of any chemical fuel. Unfortunately, our primary use of them is in thermal engines, whose efficiency is limited by Carnot'...
7 votes
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How does (E)CA glue ("super glue", "crazy glue", etc.) cure?

I use CA glue† very frequently in my shop, but I'm not entirely sure how it works. I've noticed three main modes of curing, I've emphasized the key observations: When dispensed, it will remain fluid ...
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7 votes
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Application of Le Chatelier's principle

I have the following problem: The following reversible system is at equilibrium: $$\ce{P_{4(s)} + 6Cl_{2(g)} <=> 4PCl_{3(l)}} $$ What happens with the equilibrium if $\ce{P_4}$ is added. ...
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Why does entropy increase in reactions that make more molecules?

I used to understand this (more molecules ⇒ more degrees of freedom), but do no longer, because the total number of atoms is conserved, so translational d.o.f. should just be turned into internal d.o....
7 votes
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Why does diethylmethylamine have such a low melting point?

According to PubChem, diethylmethylamine has a remarkably low melting point of $-196.0\ \mathrm{^\circ C}$. This is substantially lower than the melting points of dimethylethylamine ($-140.0\ \mathrm{^...
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Distilling milligram quantities of oil like it's late 1970s

In a currently retracted* manuscript by Tomas Hudlicky [1, Retraction Watch] the following has been noted: Fifty years ago professors took an active part in all laboratory instructions and they ...
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Relativistic contraction of orbitals

I am confused about what seems to me two very different explanations for the relativistic contraction of orbitals for heavy elements. My teacher told me that since 1s electrons in heavy elements ...
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385 views

Cloud-based molecular modeling software

I’m an IT Acquisitions and Licensing specialist researching well-supported cloud software alternatives to Fujitsu’s molecular modeling SCiGRESS. I am coming in with a tech background, but little to ...
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