45

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 to the number of interlocked components) as one shown below (Ref. 1): (The diagram is from Reference 1) This specific molecule (8; an “impossible” [2]rotaxane)...


34

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 reach a point where the concentration of A is so small that it can be considered null for your applications. If, however, you dilute the solution, take a sample, ...


27

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 component. Known to occur naturally on Earth as a high-pressure phase trapped in diamonds, Ice VII is a stepping-stone to the macromolecular and superionic ...


13

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 senior respectable user here has written an entire monograph on this topic. Suppose you have a NaCl solution, and so called "pure water"*, matter how ...


13

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 wikipedia page on Borole): Natural Bonding Orbitals of Borole. Structure optimised using ORCA BP86-D3BJ and def2- TZVPP basis set. The calculated occupencies of the ...


12

The current methods employed for synthesis fall into the following three categories1: Chemical synthesis Biochemical methods Isotope exchange reactions Chemical Synthesis: Most chemical syntheses involving $\ce{^14 C}$ are done with Grignard reagent and $\ce{^14 CO2}$ or $\ce{^14 CN-}$. As an example, Benzene-14 is synthesized as such2: Basic preparatory ...


9

Note that there is the law of mass and energy conservation, but there is no law about volume conservation. Molecules of matter are in eternal motion. Molecules of gases move freely by flying between collisions. Nitrogen or oxygen molecules of air have an average speed of a supersonic fighter, colliding at rate typically 10 billions collisions per second, ...


8

SMILES doesn't define a particular order in which the atoms show up in the string. Hence the position in the molecule where software starts printing will determine the string. E.g. for CO2: Ketcher prints C(=O)=O (starts with C and considers one of the O's a branch) MarvinJS prints O=C=O (starts iteration with O, hence no branching) Both of these ...


8

Unequivocally yes! If your solute is something of which you can identify a single molecule in a macroscopic solvent sample (let´s say a fluorescent dye), then you can dilute down to zero, and be sure about it. (For the nitpickers: This can be done in a finite number of steps, if you split the solution in two after each step, and keep diluting the part which ...


8

Simply for the beginners in organic chemistry, this explanation of aromaticity is good enough: An aromatic (or aryl) compound contains a set of covalently bound atoms with specific characteristics: A delocalized conjugated $\pi$ system, most commonly an arrangement of alternating single and double bonds. Coplanar structure, with all the contributing atoms ...


7

I think your notation of "Changing one atropisomer to another requires bond breaking (in some cases the removal and reattachement of steric groups, according to my understanding)" is not correct. To my knowledge, the free rotation of one single bond of an atropisomer is not restricted by connecting bond(s). I think you get confused by some ...


7

Ring-opening polymerization, in particular using olefin metathesis which keeps growing closed rings in the absence of linear olefins, will produce macrocycles that are intertwined to form a pseudo cross-linked network, globally insoluble polymer. This can be later "un-crosslinked" by resuming the metathesis reaction with linear olefins.


7

Widely used terminology might not match what an examination wants It is possible that your question wants the answer 8 in this context, but whether this answer would be widely accepted by anyone familiar with bonding theory is doubtful. In the early days of theories about bonding Lewis described bonds as consisting of two shared electrons. You are probably ...


7

Not all data are provided in explicit form. They are often not frequently needed and can be often deduced from other data with using of high school knowledge. You can calculate the volume occupied by 1 water molecule ( in average ) from the water molar mass $\pu{M}$, water density $\pu{\rho}$ and the Avogadro constant $N_\mathrm{A}$ as $$V=\dfrac{M}{\rho \...


6

TL;DR: It's 2 (2,2'‐dibromo‐6,6'‐diiodo‐1,1'‐biphenyl) and maybe even 3 (2,2'‐diiodo‐1,1'‐biphenyl; 2,6‐dimethyl‐1,1'‐biphenyl) at higher temperatures. Introduction According to the IUPAC gold book chirality is defined the as the geometric property of a rigid object of being non-superposable on its mirror image. Orr in other words, such an object has ...


6

The bond lengths given in your example tables are average bond lengths. That means, the actual bond length in given compound can be larger or smaller than the given value. Keep in mind that bond lengths are not just proportional to sizes of atoms involved making them. As pointed in the other answer, they are determine by other factors as well, which is a ...


6

According to the new recommendations of IUPAC nomenclature rules, when choosing the senior parent structure, you have to first consider the senior parent structure, which has the maximum number of substituents corresponding to the principal characteristic group or senior parent hydride in accord with the seniority of classes (functional groups). Then, if ...


6

When naming a organic compound, S/R-notation comes if there is a chiral atom present. The S/R-notation always accompanies a numerical such as (2S,3R)- where the numerical refers to the chiral carbon position in the molecule according to the IUPAC numbering while R and S representate the orientation of the chiral atom according to the Cahn–Ingold–Prelog ...


5

This chemistry was first described in this 1960 JACS paper here. The first step is cleavage of the $\ce{Br-CCl3}$ bond to give $\ce{Br^.}$ and $\ce{^.CCl3}$. The second step is $\ce{Br^.}$ abstracting a proton from toluene to give $\ce{HBr}$ and a benzyl radical. The third step is the $\ce{^.CCl3}$ radical abstracting a proton from toluene to give ...


5

For centro-symmetric space groups such as this one, the origin coincides with the center of inversion. You can see this specifically for this group if you look at symmetry operation (13): $$\overline{1} \mathrm{\ at\ } 0,0,0$$ Of course, there an an infinite number of origins in an infinite lattice because of the translational symmetry. In the tables, the ...


5

You are indeed correct that the elemental molecule $\ce{H2}$ is the most abundant molecular species in the universe by far.[1]. In order to answer your question Is water the most common multielemental compound? I only focus on neutral species, of which around $50\%$ are in molecular, i.e. multiatomic form.[2] In this category, second only in total ...


5

Something like a zero concentration is achieved in the vapor phase in some materials. In this answer the triple-point vapor pressure of gallium is identified as so low that a measurement thereof defaults to zero with a high probability.


5

The RKR method determines the classical turning points $r_{\pm}$ of the potential energy based on knowing experimentally determined spectroscopic constants. ( Rydberg, 1931, Z. Physik. v73,376, Klein, 1932 Z. Physik. v76, 226, Rees Proc. Phys. Soc.(Lond.) 1947, v59, 998.) The energy equation takes the usual form. Parameters all in cm$^{-1}$, distances in m, ...


4

I agree with the redditors that the answer is likely a polyoxometalate. $\ce{Na48[H_xMo368O1032(H2O)240(SO4)48] · \text{ca.}~1000 H2O}$ aka $\ce{\{Mo368\}}$ (core: $M \approx\pu{60.7 kDa},$ dimensions $\approx \pu{2.5 nm} × \pu{4.0 nm})$ is the primary candidate [1]: Figure 2. Structure of 1a in crystals of 1 in polyhedral (a) and ball and stick (b) ...


4

In the painting "Dream Caused by the Flight of a Bee" by Salvador Dali, among other strange items, we may see a fish flying in midair. There is also one in the drawing "Big Fish Eat Little Fish" by Bruegel the Elder. One may conclude that there is a flying fish in every picture out there. One may even publish a paper to that effect. But I believe you see the ...


4

Technically liquid, but close to the boiling point and a bit nasty to work with, is carbon disulfide. It melts at about -112°C and boils at +46°C.


4

Hypothetically, I think limitation for zero-dilution would be when you take a sample of diluted sample the possibility of having a solute molecule in there should be zero. To achieve this goal, the concentration of your solution should be less than $10^{-24}$ in power $\left(\frac{1}{6.022 \times 10^{23}}=1.66 \times 10^{-24}\right)$. To do so, if you have $\...


4

It is true that until recently, the syntheses of primary anilines mostly rely on the reduction of corresponding nitroarenes. However, recent publications allow the synthesis of primary anilines or their derivatives in laboratory. One such method is Buchwald–Hartwig amination: The palladium-catalyzed cross-coupling of amines and aryl (pseudo)halides, now ...


4

You appear to have an understanding of R/S nomenclature. The numbers, 2 and 3, are simply the carbons that are stereogenic. In the compounds shown below, the carbon bearing the hydroxyl group is C2 and not C3 because the hydroxyl group has priority over the bromine. Of course, carbon numbering begins at the terminus of the chain proximate to the hydroxyl ...


3

This reaction is already in the literature (peer-reviewed paper), so I don't want to change any outcome already explained by Waylander. But, I like to explore the reaction a bit more for the benefit of novice students of organic chemistry. The reaction seemingly follows the same mechanism as that of a general free radical reaction: Initiation; propagation; ...


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