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1500 questions
21
votes
4 answers
Is an isobar the same as an isotope?
I am a little bit confused about what an isobar is. Its online definition is that it's an element with the same number of neutrons but a different number of protons from an element $\ce{X}$.
To me, it doesn't make sense from the get-go, because…
SpacePotato
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21
votes
2 answers
Why is a singlet state called singlet and a triplet state called triplet?
I kind of get the idea of singlet and triplet states. But why are they called singlet and triplet (what is the single and what is the triple in these cases)?
I feel that I am missing something obvious!
hat
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21
votes
1 answer
Regioselectivity of epoxide hydrogenation using Pt versus Ni catalyst
What conditions are applicable for the transformations X and Y, respectively?
(a) $\ce{LiAlH4}$, and $\ce{NaBH4}$
(b) $\ce{NaBH4}$, and $\ce{BCl3}$ followed by $\ce{NaBH4}$
(c) $\ce{LiAlH4}$, and $\ce{AlCl3}$ followed by $\ce{LiAlH4}$
…
Iceberry
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20
votes
2 answers
Does CN4 with the following structure exist?
I am a mathematician, not a chemist, so my questions are rather combinatorial. I am intrigued by the possibility of the following binary compound:
$$\ce{\overset{-}{N}=\overset{+}{N}=C=\overset{+}{N}=\overset{-}{N}}$$
which ought to be isoelectronic…
Thomas Forster
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20
votes
2 answers
Why do we not generally have "enneane"?
Most numerical prefixes are based on Greek roots, but for "nine" we use the Latin root instead which seems inconsistent. Thus, for instance, "nonane" instead of "enneane", or in mathematics "nonagon" instead of "enneagon" (although here the Greek…
Oscar Lanzi
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20
votes
2 answers
Why is cis-1,2-dichloroethene more stable than trans-1,2-dichloroethene?
Why is cis-1,2-dichloroethene more stable than trans-1,2-dichloroethene?
Usually, trans compunds are more stable than cis ones, due to less strain and its non-polarity. But, in this case it's quite the opposite. I tried to search the reason behind…
Iceberry
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20
votes
2 answers
What are the crystals that have formed around the top of a conc. nitric acid bottle?
I was looking through my chemicals cupboard and found that this decades-old bottle of conc nitric acid had grown a beard. I can't think of any reaction between (presumably) $\ce{NO2}$ and any airborne substance that could produce this. Any ideas?
Will Higgs
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20
votes
4 answers
How many Ga atoms are connected to one As atom in solid gallium arsenide?
In Boylestad and Nashelsky's Electronic Devices and Circuit Theory, the structure of GaAs is shown as follows:
Arsenic is shown making five covalent bonds to neighbouring gallium atoms.
However, I recently also saw an alternative depiction in…
user31782
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20
votes
2 answers
Is borazine aromatic?
I came across this structure which has got pi bonds only in its canonical forms (which are also unstable compared to the Ist structure), is it aromatic?
Also, is it compulsory for an aromatic compound to contain a carbon ring? Can't a conjugate…
Kirti Agrawal
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20
votes
3 answers
Why doesn't TEMPO react with itself?
TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl, or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) has the following structure:
Given that it's a free radical, why doesn't it react with itself, despite being capable of reacting with other radicals in…
I. Kor
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20
votes
1 answer
What are the CIP rules for cyclic substituents?
Here's what I read on Wikipedia (section "Cycles"):
To handle a molecule containing one or more cycles, one must first expand it into a tree (called a hierarchical digraph by the authors) by traversing bonds in all possible paths starting at the…
stoic-santiago
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20
votes
3 answers
Why is the rate of reaction of polar EAS favored by inductive effects and the rate of less polar EAS reactions through hyperconjugation?
1. Reactions involving strong electrophiles (nitration) are
said to be governed
by
Inductive effects thus the order of nitration is
D>C>B>A
2.Chlorination is a less polar reaction thus chlorination said the be governed…
Avyansh Katiyar
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20
votes
1 answer
What is three dimensional aromaticity?
I have recently come across a statement which states:
The relative stability of the 1,3-dehydro-5,7-adamantanediyl dication is ascribed to its three-dimensional aromaticity. [1]
My understanding of aromatic nature is, that the molecule must be…
Chakravarthy Kalyan
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20
votes
4 answers
During the development of aspartame, why was the methyl ester chosen?
One frequent argument against the safety of the synthetic sweetener aspartame is that it can be hydrolyzed, with one of the hydrolysis products being methanol, which is known to be toxic. Of course, usually not much aspartame is added in food anyway…
user95
20
votes
6 answers
Organic Structure Challenge
Recently we had this challenge in our Organic Chemistry Department.
I was not involved in it but I thought it might be interesting for the SE Chemistry site, so here it is.
Propose a structure for C20H18 with the longest IUPAC name.
Following rules…
Raoul Kessels
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