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1500 questions
15
votes
1 answer
Why/how is blood red? (colours of hemoglobin)
Oxyhaemoglobin is red, deoxyhaemoglobin is bluish-purple, and carboxyhaemoglobin is a cherry red colour.
Evidently in the porphyrin around the iron molecule in heme there is a conjugated $\pi$-system which could account for the colour, but how…
James Harrison
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3 answers
When did the atom theory become indisputable?
We know that the Greeks were the first scientists (or better, philosophers) to introduce the idea that matter is made up of little “chunks”, and they named these chunks “atoms”. This idea that matter comes in discrete small pieces was termed wrong…
Hosenberg
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15
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6 answers
Conducting current in electrolytes
I keep trying to figure out how current is conducted through an electrolyte but all I can find are incomplete answers. They say the ions conduct, but the specifics are poorly explained or absent.
I understand that if you, for example, put sodium…
Void Star
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Electron density definition of single, double, triple bonds?
I was reading this question and the answer by user EricBrown to it, and this got me thinking about covalent chemical bonds.
The way I was always taught is that a single bond contains 2 paired electrons, a double bond 4 etc (The Lewis dots drawings…
Michiel
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15
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1 answer
Why is KI oxidized by H2SO4, whereas NaBr isn't oxidised?
My textbook says that alcohols react with sodium bromide and sulphuric acid to form the corresponding alkyl bromides. At the same time they also mention that sulphuric acid mustn't be used with potassium iodide ($\ce{KI}$), because $\ce{HI}$ formed…
Shahbaaz1104
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4 answers
Is LiOH a weaker base than NaOH?
Is $\ce{LiOH}$ a weaker base than $\ce{NaOH}$?
Note: I'm not interested in "why," but rather what the "real" $\mathrm{p}K_
\mathrm{b}$ values are.
$$
\begin{array}{lcc}
\text{Data for Alkali Metal Hydroxides} \\
\hline
\text{Cation} &…
MaxW
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Rotation around CC bond in 1,2-dioxetane: transition states and local minimum structures
TLDR:
What: Potential energy surface associated with rotation around CC bond in the ring-opened version of 1,2-dioxetane.
How: State average(4)-CASSCF(12,10)/VTZP constrained geometry optimizations keeping OCC'O' and one HCC'O' dihedral angle fixed.…
Yoda
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15
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1 answer
Why is the 5d orbital instead of the 4f orbital filled in lanthanum?
For orbitals with the same value of $n + l$ (e.g. the $\mathrm{3d}$ and $\mathrm{4p}$ orbitals), we usually expect the orbital with the lower value of $n$ to be filled earlier. Hence, for example, the $\mathrm{3d}$ orbitals are filled before the…
Diyanko Bhowmik
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Alkane deprotonation by organolithiums
Butyllithium isomers are all stored in alkane solvents. Theoretically, equilibrium should (given enough time) lead to formation of mostly n-hexyllithium in the case of n-BuLi stored in (mostly) n-hexane, I believe. I understand that the kinetics of…
SendersReagent
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15
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1 answer
What does the eta notation mean in the naming of a transition metal complex?
I am reading a paper (Gutel et al., J. Mater. Chem. 2007, 17, 3290-3292) and I have come across the following reaction:
In organic solvents, the decomposition under mild conditions of
…
Andrew
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1 answer
Acid catalysed synthesis of ethyl ethoxymethylenemalonate
One synthesis of quinolones begins with the formation of an ethyl ethoxymethylenemalonate, as seen in this Organic Syntheses paper.
I've been asked if the malonate derivative would be formed if methylmalonate was treated with trimethyl orthoformate…
CHM
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15
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2 answers
Why does the ink on my whiteboard move?
...or at least I thought so, when I saw that the ink that was on my whiteboard last night became really messed up the next day.
The image below shows my whiteboard before (on the left) and after (on the right). The time span was one night.
As you…
rhyaeris
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1 answer
Kinetic Isotopic Effect in EAS
It is observed that rate of reaction of two isotopologues of benzene, $\ce{C6D6}$ and $\ce{C6H6}$, is the same for electrophilic aromatic reactions, as the deprotonation is not the rate limiting step. Instead the carbocation is usually limiting.
Do…
Mrigank
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2 answers
Why is this compound named resorcinol?
Substituted phenols or polyhydroxy phenols have their general name apart form IUPAC names. The general names comes from the source it is found like:-
Catechol (1,2-dihydroxybenzene)- obtained from catechu
Cresol (methylphenol) - obtained from…
Nilay Ghosh
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15
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1 answer
Are there any examples of nuclear spin isomers having consequences for chemical reactivity?
Ortho- and parahydrogen are two forms of the $\ce{H2}$ molecule that are distinguished by their pairing or antipairing of nuclear spins, giving rise to metastable singlet (ortho-) and triplet (para-) states. This constitutes an example of nuclear…
Richard Terrett
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