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51 votes
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Why is an S-S bond stronger than an O-O bond?

TL;DR: The $\ce{O-O}$ and $\ce{S-S}$ bonds, such as those in $\ce{O2^2-}$ and $\ce{S2^2-}$, are derived from $\sigma$-type overlap. However, because the $\pi$ and $\pi^*$ MOs are also filled, the $\pi$...
orthocresol's user avatar
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51 votes
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Do molecules with bridges through rings exist?

I'm not sure about the existence of molecules with bridges through rings. However, there are several publications of synthesis of molecules mimicking wheels and axles ([2]rotaxanes; The “[2]” refers ...
Mathew Mahindaratne's user avatar
36 votes
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Is it possible to achieve a level of "truly zero" concentration?

It depends how you dilute it. If you take an aqueous solution of A and just add pure water (absolutely 100% water), the concentration of A will never quite be null. In this case however, you will ...
Raphaël's user avatar
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30 votes

Do molecules with bridges through rings exist?

A variation on this theme is Ice VII, in which two cubic ice structures are intertwined with hydrogen bonds from each component structure passing through the hydrogen-bonded rings formed by the other ...
Oscar Lanzi's user avatar
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27 votes
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Why do the atoms in molecular models have the colors they have?

There's an interesting article here - Illustrating Atoms and Molecules - that discusses atom colors: In 1865, the chemist August Hoffman gave a Friday Evening Discourse at London’s Royal ...
gilleain's user avatar
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21 votes

What is this fluorinated organic substance?

The name of the compound is 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (CAS #: 140681-55-6), which is commonly known as Selectfluor, a trademark of Air Products ...
Mathew Mahindaratne's user avatar
20 votes
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Why do we not generally have "enneane"?

Perhaps not a complete answer, but this might put you on the right track. It looks as though a lot of the system we have today grew out of recommendations made by August Wilhelm von Hofmann in a paper ...
Tyberius's user avatar
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19 votes
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Why do methane molecules have 15 degrees of freedom?

15 is there because you have 5 atoms which can move independently, and we live in a 3D space, and $3\ \times\ 5\ =\ 15$. 3 of these are translational degrees of freedom, which you seem to agree with, ...
Ivan Neretin'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

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
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Complex organic molecules

tl;dr: two different definitions. Astronomy: multiple carbon atoms in molecule. Chemistry: polymer Interestingly enough, after reading about COMs here, as well as reading the Wikipedia page and the ...
JSCoder says Reinstate Monica's user avatar
18 votes

What is kekulization (in RDKit)?

This is a method to generate alternate Lewis structures of the same molecule. Here are two examples from the cumulative dissertation by Sascha Urbaczek[1]: If you were to search for the left molecule ...
Karsten's user avatar
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16 votes
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What is quasi-aromaticity?

In general, we can describe a quasi aromatic compound as a compound, which is ionic in nature with a counter ion, and the $\pi$ electrons in such compounds follow Huckel's rule ($4n+2$). In other ...
Mathew Mahindaratne's user avatar
15 votes

Is it possible to achieve a level of "truly zero" concentration?

For an analytical chemist, the concept of zero concentration does not exist. The concentration cannot be exactly 0! Only a limit of detection can be developed in terms of statistics. This is why a ...
AChem's user avatar
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14 votes
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Do molecules containing only carbon exist?

They do form. Besides fullerenes, there are carbon molecules with varying numbers of atoms around some stars[1]. Vaporized graphite in such environments produce chains of 3 to 30 carbons and larger ...
Oscar Lanzi's user avatar
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14 votes
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What is this fluorinated organic substance?

That is generally known as Selectfluor, a source of electrophilic fluorine. The zig-zag line is a 2-D representation of the third ethylene $\ce{-CH2-CH_{2} -}$ unit that links the two nitrogens. more ...
Waylander's user avatar
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14 votes
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Why is borole not considered aromatic

A very basic way to do this would be to draw a diagram that shows the p-orbitals going above and below the plane. For Borole, the bonding orbitals would look like as shown below (taken from the ...
Safdar Faisal's user avatar
14 votes

Can sugars dissolve in liquid ammonia?

Can sugars dissolve in liquid ammonia? Yes, according to Ref.1, liquid ammonia is used to extract sugars in sugar-beet chips: 5.88 kilograms of sugar-beet chips having a moisture content of 5.4 ...
Mathew Mahindaratne's user avatar
14 votes

Are physical space filling molecular modelling kits still available anywhere?

Note, CPK (for Corey–Pauling–Koltun) is a colour scheme, i.e., a convention to symbolize atoms of carbon in black, oxygen in red, nitrogen in blue, etc. which took ...
Buttonwood's user avatar
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13 votes

Why do we not generally have "enneane"?

I believe Tyberius gave an extremely reasonable answer for the question and it deserves to be the best answer. I just want to provide some supporting facts for his argument. For example, there are a ...
Mathew Mahindaratne's user avatar
13 votes
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How do I visualise bicyclo[4.4.1]undeca-1,3,5,7,9-pentaene?

This compound is 1,6-methano[10]annulene, and a classic example of an unusual compound displaying aromaticity. Aromaticity requires the pi-system to lie in a plane. One might speculate that [10]...
jerepierre's user avatar
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12 votes

How does a molecule search work by drawing in visual editor?

Usually, structure search is implemented using a graph model. For example, let's take cyclohexane. On screen this is a hexagon - but this is converted on the server to a simple atom/bond graph model ...
gilleain's user avatar
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12 votes
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How are organic compounds with radioactive atoms synthesized?

The current methods employed for synthesis fall into the following three categories1: Chemical synthesis Biochemical methods Isotope exchange reactions Chemical Synthesis: Most chemical syntheses ...
Aniruddha Deb's user avatar
12 votes

Are physical space filling molecular modelling kits still available anywhere?

Is there any current source of those 3D CPK kits? You have to distinguish space-filling and semi-space filling, see below: For semi-space filling, many ball-and-stick models also have pegs instead ...
Karsten's user avatar
  • 40.7k
11 votes

Does NaOH react with K to form NaOK or KOH?

The question: Will $\ce{NaOH + K}$ form $\ce{NaOK}$ or $\ce{KOH}$? This is a redox reaction regardless of what species $\ce{K}$ would react with. The answer is two-fold: (a) Having potassium added to ...
Mathew Mahindaratne's user avatar
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
  • 71.4k
11 votes
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Which biphenyl is optically active?

Biphenyl 2 is the only optically active compound here. These stereoisomers are due to the hindered rotation about the 1,1'-single bond of the compound (Ref.1). Biphenyl 3 is not optically active, ...
Mathew Mahindaratne's user avatar
10 votes

What is the difference between ''1 C atom and 1 mole of C atoms?''

What is the difference between one egg and one dozen eggs? A dozen is simply a certain count, in this case 12, that is rendered as one unit for our convenience. Avogadro's number s just the same ...
Oscar Lanzi's user avatar
  • 58.6k
10 votes

What would be the name of this compound?

I think it is Cubane ($\ce{C8H8}$), a synthetic hydrocarbon molecule (Wikipedia), which has synthesized using following scheme: I am confident about that because your teacher had said that there wasn'...
Mathew Mahindaratne's user avatar
10 votes

d-Menthol vs dl-menthol: Does an enantiomer and its racemic mixture have different melting points?

In stereochemical vocabulary, a racemic mixture (racemate) is one that has equal amounts (50:50) of left- and right-handed ($d$- and $l$-) enantiomers of a chiral molecule. According to Wikipedia: ...
Mathew Mahindaratne's user avatar

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