15

No, for three reasons: Firstly, you need a relatively large molecule and/or a high viscosity and/or a strong shear/extensional flow, before the molecule even notices that it´s in a nonuniform environment. The molecule, if it has an elongated form, will then align perpendicular to the normal vector of that flow field. That only occurs for sufficiently ...


14

Mirror images The very first definition of a chiral molecule is one where it is not superimposable on its mirror image. Therefore, one of the most straightforward ways to determine chirality is to construct the molecule and its mirror image (perhaps via a model), and then to see whether they are superimposable. Symmetry elements A fully equivalent ...


13

Circularly polarized light is like a helix that twists through space. The two components are mirror images of each other. Now, every molecule interacts with both the left-handed twisting light and the right handed twisting light. The interactions differ. Every molecule, in different orientations, interact differently with the left-handed and the right-handed ...


10

The enantiomers 1a and 1b can have their double bonds defined by CIP rules 1a and 5. Rule 1a dictates that CH3>H while Rule 5 has R>S. Thus, 1a has an E-double bond and 1b is of the Z-configuration as exemplified by the red bonds. This issue has been addressed previously on this site. Addendum: While the enantiomers 1a and 1b (vide supra) have their double ...


10

The given answer is wrong in many ways: 4 did not satisfy both criteria C and E, because it is not a chiral compound to begin with. 10 did not satisfy the criteria D, because it does give a precipitate with iodine in presence of $\ce{NaOH}$. That gives only 5 in given answer to satisfy all criteria. Let's eliminate given compounds in systematic order: ...


10

Carbons #2 and #4 are chiral centres themselves. There are four possible diastereoisomers: If C2 and C4 have different configurations, which is the case in molecules A and D, then C3 is termed a pseudoasymmetric centre and labelled with a small 'r' or 's'. These diastereomers are meso compounds: although they contain chiral centres, they are not chiral, ...


9

In short: if the direction of stirring were a both reproducible and highly significant parameter for the synthesis of chiral molecules, the manufacturers would offer a back- and forward direction of stirring by default all across their stirrers. But no, I'm not aware that there is such an effect. Note, however, beside the stirring plate in the (small scale) ...


8

Technically, this double bond should not be labelled as (E)- or (Z)-. It is what is known as an enantiomorphic double bond, for which the proper stereodescriptors are seqCis and seqTrans. This is described in P-92.1.1 in Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Notice that for your compound, we have $(\...


8

These two intriguing papers conclude chiral environments can be induced by directional stirring, where the direction of the chirality depends on the direction of stirring. And other work has shown that chiral environments steer the direction of chiral synthesis.* So: If [direction of stirring] -> [direction of chirality of environment] -> [direction ...


8

Part 1 Are there any molecules lacking plane of symmetry/center of inversion but that are achiral due to presence of an axis of improper rotation? Yes, although such examples are very rare. In general, the point groups $S_{2n}$ $(n \geq 2)$ are where you should look. These molecules have a $S_{2n}$ rotation axis, but no plane of symmetry, and no inversion ...


7

Edited version: I originally wrongfully assumed these two structures are not geometrical isomers of the double bond, because it is a trisubstituted double bond with at least two identical groups (although they have two different spatial arrangements as R- and S-designations). As a result, I conclude that the two compounds cannot be distinguished by (E) and (...


7

I think that correct answer should be 5 and 6 only, because: 12 will produce terephthalic acid, instead of benzoic acid as it possess two benzylic-H (also given by 7). 4 and 10 doesn't satisfy statement C and D, as you've mentioned.


6

Yes, spatial configuration of attached groups matters. Meaning different stereo configuration of $C_1$ and $C_3$ may render $C_2$ either chiral or not: Also because you have more than 1 stereo center you're not limited to just enantiomers, you can get diastereomers - the molecules will be different even though they're not mirror images of each other:


5

It indeed is achiral, because the red dot is the center of symmetry, hence it is superimposible with its mirror image. Having an internal plane of symmetry is not the only criterion, the presence of a centre of symmetry also leads to the compound being achiral.


5

Nitrogen will always perform nitrogen inversion if it is not configurationally fixed due to steric or electronic reasons. Fixing the configuration sterically could be achieved, for example, by a polycyclic compound as in 1 below. Fixing the configuration electronically is exemplified by the amide 2 (note that the amide is achiral; the nitrogen is forced into ...


4

On a larger scale, the direction of stirring can be used to optimize homogenization of complex mixtures. For instance, paint-like products can be mixed with a propellor-type blade. When the direction of rotation orients the blade pitch so as to force liquid down and around, a vortex is created which may dip so low as to allow air to be incorporated into the ...


4

So I thought about this for a bit and I think I have an answer. Be warned, I might be wrong. The inversion process involves a conversion from $\mathrm{sp^2}$ to $\mathrm{sp^3}$. So $\mathrm{sp^2}$ hybridization increases angle between these bulky groups, which would be in fact favorable. Hence the low activation energy.


3

Originally, both of us, andselisk and I, thought you are taking about a plain which goes through all four groups ($\ce{H-H-Cl-OH}$ squire). It is a forbidden plane when it come to symmetry of a compound, if it had been the case. Fortunately it is not the case. We later realized after Mithoron's comment that the plane you are talking about actually goes ...


3

Barriers to intramolecular motions, which lead to inversion, are intimately related to the configurational identity of a molecule ($\ce{XY3}$). These barriers turn out to be most sensitive to changes in $\nu_2$ (the frequency of symmetrical deformation vibration) and $\ce{Y-X-Y}$ angle ($\alpha$) of $\ce{XY3}$ (Ref.1). The inversion is assumed to take place ...


3

The short answer to your question Under conditions that inhibit inversion, an amine that has three different groups attached is chiral. The above applies not just to tertiary but also to secondary amines. Now, why inhibit inversion? Why does it make a difference? As mentioned by Zhe (and mentioned in Newton's answer) in the comments: Tertiary amines can ...


3

Your assumption that $\ce{[Ni(gly)2]}$ shows optical isomerism is incorrect: the complex is square planar in nature and has a plane of symmetry (the plane passing through all the atoms). It is thus achiral and does not have any optical isomers. It does show geometrical isomerism though, as the ligands are not symmetric with reference to each other.


3

Dextrorotatory = d = (+). Levorotatory = l = (-). These terms describe the absolute sense of rotation in an optically active substance. D and L are older terms for the sense of chirality that can be traced back to dextro- or levorotation of glyeraldehyde. The actual compound may have the same or opposite sense of rotation, but the assignment is determined by ...


3

Skipping axial and helical chirality altogether, no to point #2: there are examples of atom centred chirality without a carbon atom in the centre. The careful oxidation of thioethers may yield chiral sulfoxides: (Han et al., Chem. Soc. Rev. 2018, 47, 1307-1350, doi 10.1039/C6CS00703A). Here, chiral requires just the two carbon substitutents to differ, ...


3

TLDR: They deal with similar, but different, notions of "chirality". First, the definitions, from the IUPAC Gold Book: asymmetric carbon atom The traditional name (van't Hoff) for a carbon atom that is attached to four different entities (atoms or groups), e.g. Cabcd. chirality centre An atom holding a set of ligands in a spatial arrangement ...


3

To deal with just question 2 (which is not a complete picture as chiral centres may be non-carbon atoms and some molecules are chiral even without having an individual chiral centre). A carbon atom with 4 different things attached to it is necessarily chiral because of its geometry. The bonds around the carbon will form an approximate tetrahedron and any ...


2

This really doesn't answer the question, but the discussion is too long for comments. The question only makes sense if you start with a mixture that has optical activity. Let's call the concentration of the starting enantiomer $x$ and the other enantiomer $y$. Optical activity is unfortunately, not a concentration, so we need a definition to make the two ...


2

First, for simplicity, I am assuming that the initial substrate (2-iodobutane with radioactive iodine) consists of only one enantiomer. How would 2-iodobutane lose its optical activity (it still has a chiral $\ce{C}$)? In $\mathrm{S_N1}$ mechanism, there is 50% inversion and 50% retention, so a racemic mixture starts to form which decreases the optical ...


2

They are achiral. If you take the mirror image (first picture) and rotate 180 degrees (second picture), you can overlay them. Images made with Avogadro


2

Here are the six structures that your source is probably referencing.


2

Here I have a compound with 2 chiral centers. There is only inversion at Carbon with iodine undergoing $\mathrm{S_N2}$ reaction. The second carbon does not undergo $\mathrm{S_N}$ reaction. There is no change in its configuration. Example 1 In the example below , [Ref : https://en.chem-station.com/reactions-2/2016/05/neighboring-group-participation.html] ...


Only top voted, non community-wiki answers of a minimum length are eligible