Refers to the spatial arrangement of atoms in a chemical entity.

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Stereochemical aspect of heating of cyclohexane-1,2-diol

Does stereochemistry play any role in the heating of Cyclohexane-1,2-diol? If I remember correctly, different products are formed depending on whether the diol is cis or trans. (I think the products ...
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0answers
17 views

Stable conformers of piperazine

which conformer stable of piperazine, when hydrogen of N in axial or in equatorial, or lone pair? why?
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1answer
33 views

Oxymercuration Demercuration Mechanism doubt

I'm having a doubt on the mechanism of oxymercuration Demercuration reaction. How does the reaction, initially heading towards anti addition(after cyclic transition state formation) ,get spoiled by ...
2
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0answers
28 views

Assigning R/S stereochemistry of a cyclic molecule

I've been dealing with assigning stereochemistry and I seem to be doing okay, but I've come across a molecule that I've found a little tricky to deal with. I've identified three stereocentres, ...
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1answer
39 views

How to get a protein's dihedral angles ordered by variance?

The setting: I want to simulate protein docking and let some dihedral angles vary, but in order to keep it low-dimensional I have to select those which are most likely to change. What I've thought of ...
6
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2answers
373 views

Is 2-bromobutane chiral?

My textbook says 2-bromobutane is chiral, but it look like it will form superimposition mirror image
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1answer
193 views

Boiling and melting point of trans- and cis-but-2-ene

The boiling point of trans-but-2-ene is lower than that of its cis isomer but the melting point of the former is higher than the later. Why is it not following the same order? Is there any factor of ...
2
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1answer
86 views

How many stereogenic centres are there in discodermolide? [closed]

It is generally said that carbon-carbon double bonds cannot behave as stereogenic centres but the above molecule contains three such centres. Can somebody please point out all the stereogenic centres ...
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2answers
154 views

Is tetraammine dichloro cobalt (III) an optically active compound?

Is $$ \text{Co}[{(\text{N}{\text{H}}_{3})}_{4}{\text{Cl}}_{2}]$$ optically active? If so, write its stereo-isomers. I know that for a compound to be optically active, it should ...
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2answers
328 views

Are all amino acids except glycine chiral compounds?

Specifically, I was thinking of the case where the R group is a carboxylic acid functional group or an amine group. Then there would not be a chiral carbon atom. Is there a restriction on what can be ...
2
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2answers
235 views

Whats the H-C-H bond angle in ethene?

The carbon is $sp^2$ hybridised and is therefore planar and should also, theoretically be 120$^o$. However, VSEPR theory suggests that the pi bond would "need more space" due to greater electron ...
10
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1answer
452 views

Why six C atoms are usually seen in cyclic compounds?

When it gets to Carbon-based molecules, one very possible structure when there are more than six C atoms is the hexagon; though not mostly perfect, it emphasizes that six Carbon atoms tend to bond ...
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2answers
618 views

Endo rule for the Diels Alder stereoselectivity

Do you agree with the stereocenter with the CF3/CN in the product? source I would have expected that CF3 is a better electron withdrawing group than CN, and therefore placed opposite the diene and ...
3
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0answers
84 views

Lactone vs Ester

With regard to stereoelectronic effects in esters and corresponding s-trans lactones why does donation into the $\sigma _{CO}^*$ orbital from an anti lone pair on the sp3 oxygen cause the lactone to ...
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1answer
214 views

Why is nitration of veratrole specific in these positions?

Why do we not need $\ce{H2SO4}$ as acid catalyst for di-nitration of veratrole? Why does the 2nd nitro group go to positions 4 or 5, following the directing effects of the methoxy-group? Doesn't the ...
2
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2answers
240 views

“Asymmetric molecules are necessarily polar”

Is a molecule with no symmetry necessarily polar? Can a polar molecule still have some elements of symmetry (i.e. mirror image is the same as itself)? I think so ... because we can have achiral ...
2
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1answer
71 views

How are the Cahn-Ingold-Prelog rules applied to chiral molecules without a stereogenic carbon center? i.e biphenyls and allenes

It's easy to apply CIP rules to chiral carbons but what about in chiral molecules without these carbon cneters like biphenyls, sulphoxides and allenes? Are they applied at all?
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1answer
3k views

What is the difference between configuration and conformation in stereochemistry?

I understand conformation to be any spacial arrangement of atoms that can be achieved through rotation of a single bond. I understand configuration to be the disposition of atoms/groups in space. ...
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1answer
1k views

What is the difference between absolute and relative configuration in stereochemistry?

I am unclear as to what the difference is - It doesn't seem to explain it well anywhere. Can you help me understand the difference between absolute and relative configuration?
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1answer
47 views

Are bond angles constant?

I'd imagine the answer to the question posed in the title is no - bond angles are not constant. Covalent bonds are not infinitely rigid; hence IR as a spectroscopic technique. If so, how can we ...
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2answers
250 views

What is a dl pair in stereochemistry?

Is it two isomers with at least one stereogenic center each but the corresponding center on the other isomer will rotate the plane of polarized light in the opposite direction. Is this applicable to ...
2
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2answers
323 views

Are all anomers diastereomers?

I am told that all anomers are diastereomers. I think this is BS. If there is a carbohydrate with only one chiral center, then changing the configuration of the anomeric carbon gives us enantiomers. ...
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1answer
93 views

Reduction of acetaldehyde from rectus and sinister faces

I am asked to consider the reduction of acetaldehyde from the re and si faces. I am also asked whether the added hydrogen (labeled H* in my picture) is pro-R or pro-S in both cases. In my attached ...
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3answers
485 views

Concept of “non-superimposable mirror image” in chirality

I didn't understand the fact that chiral objects are non-superimposable on their mirror images. I mean, if you put your right hand (apparently an achiral object) in front of a mirror, the mirror image ...
2
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1answer
84 views

Si and Re facial descriptors

I am considering the hydrogenation of 2-butanone with respect to its Re and Si faces. So if we look at 2-butanone as I've drawn below from above we are looking at its rectus face. And from below we ...
2
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1answer
105 views

Are Grignards Chiral?

Can Grignards be chiral? I've seen them drawn as ionic structures in class. I've also seen little asterisks on certain positions of Grignards (a common designation of chirality). So this begs the ...
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2answers
262 views

Dibromomethane bond angles

With regard to the above professor's claim, I disagree. Bent's rule, which states that atomic p-character is concentrated in orbitals directed toward more electronegative substituents, implies that ...
2
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1answer
79 views

Bond Angles and intermolecular interactions

It's fun to consider bond angles of molecules in isolation. For example, what is the number of different bond angles exhibited by the most polar form of $\ce{SIBrClF2}$? However, can bond angles ...
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3answers
447 views

Boat conformation: axial hydrogens

In my exam, my teacher asked me if the following is true: "The chair cyclohexane has more axial hydrogens" I did not have time to think, so I just put false. And apparently I was right. But, at home, ...
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1answer
182 views

Dihedral angle of gaseous and crystalline HOOH

Why does hydrogen peroxide exhibit a dihedral angle of 111.5 degrees in the gaseous state? And a dihedral angle of 90.2 degrees in the crystalline phase? I know that in general, there is likely to ...
7
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2answers
443 views

Utility of Bent's Rule - What can Bent's rule explain that other qualitative considerations cannot?

Does Bent's rule have any utility? I got a vehement earful for "NO." Points raised by my professor: Coulombic considerations can be used to rationalize bond angles, strengths, and lengths without ...
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0answers
66 views

Examples of intramolecular hydrogen bonding closing bond angles

Okay, we've established that intramolecular hydrogen bonding can exist in molecules, and doesn't always serve the purpose of closing the bond angle at least relative to other stereoisomers of the same ...
7
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2answers
2k views

What is Bent's rule?

I'm all bent out of shape trying to figure out what Bent's rule means. I have several formulations of it, and the most common formulation is also the hardest to understand. Atomic s character ...
7
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2answers
513 views

Why does nitrous acid exhibit (unexpectedly) different bond angles?

Data Point 1 - quantum chemical calculations http://nzc.iap.ac.cn/uploadpdf/Wang_et_al._CSB_2007a.pdf Key points in paper: There is some sort of interaction between the hydrogen and the terminal ...
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1answer
120 views

Inversion of Configuration - Opening of Epoxide

This doesn't look like a traditional inversion of configuration: At first I dismissed the textbook author as making a typo. But then I realized that this "typo" was repeated throughout the ...
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1answer
2k views

Is this disaccharide sucrose?

I want to know if the structure I drew is sucrose or an enantiomer of it. The One I Made: The one on internet:
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1answer
64 views

Gauche correction in Bensen group increment

I have difficulty understanding the use of gauche correction in Bensen group increment method to calculate the heat of formation. As an example, 4 times gauche correction (0.8 kcal / mol) is ...
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1answer
220 views

Racemic mixture of meso compound

My solution manual implied that we can have a racemic mixture of a meso compound. Is this possible? I was able to rotate the molecule to make it symmetrical. Sure, the bromination in the ...
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1answer
35 views

Enantiomers or Diastereomers?

The key tells me these are enantiomers. I however don't think they are; their chiral carbons' configurations aren't inverted - i.e. only one chiral carbon's R/S configuration changes! This ...
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1answer
32 views

Flipping a molecule vs. mirror behind compound

Why aren't these enantiomers? If you place a mirror behind the compound and look into the mirror, you get the second drawing.
2
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2answers
222 views

Why is the acyclic to cyclic rearrangement of Glucose formed via the C5 hydroxyl group?

In converting glucose from its acyclic form to either cyclic form (alpha or beta) why is the C5 hydroxyl group used instead of the bottommost hydroxyl group? Also, are these structures considered ...
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3answers
83 views

R, S Configuration and Branching - Which Path?

Which path do I take when we have a branched chiral center? None of the textbooks I've consulted adequately covers this or even provides an example problem in which there was branching. Consider ...
2
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2answers
154 views

R,S Configuration

I don't understand why this molecule is assigned S instead of R. The H is assigned a priority of 4; the methyl group on the chiral carbon gets 3; the left carbon gets 1 and the right carbon gets ...
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2answers
66 views

What is the canonical reference for studying stereochemistry?

I am well versed with all the named reactions and all of organic chemistry. I am quite weak in stereochemistry. What canonical text can I use to study this topic and connect with other parts of the ...
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2answers
4k views

How does Walter White make pure crystal meth using a non-stereospecific reaction?

In the fantastic TV series Breaking Bad, Walter White, the dying chemistry teacher, takes to making crystal meth (d-methamphetamine) by several routes. Initially, he uses the common small-scale route ...
4
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1answer
303 views

Molecular chirality and optical rotation

Why does having molecular chirality result in optical rotation? The dissymetry or chirality of molecules translates to the rotation of plane polarized light, the magnitude and direction depending on ...
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1answer
2k views

Finding chiral carbons in aromatic or cyclic compounds

I know that for a carbon to be chiral four different groups should be attached to that particular carbon. But, what about in the case of cyclic compounds? What's the method to check chirality if the ...
2
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1answer
168 views

Racemization of biphenyl compounds

How does the effect of heat and effect of substituents affect racemization of biphenyl compounds?
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182 views

Entropy and racemization?

The process of racemization of an optically compound is entropy driven and hence nature prefers a racemic mixture to an optically active one, which is consistent with the idea of the intuitive ...
11
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1answer
4k views

Why is the Wittig reaction syn stereoselective?

This question is meant for a simple (not stabilized) Ylide. Consider the classical mechanism for the Wittig reaction given on Wikipedia I am not able to understand why only one intermediate has ...