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Questions tagged [stereochemistry]

Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.

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2 votes
0 answers
130 views

stable conformation of 2,3-dimethylsuccinic acid

I was researching for answering this question on Kolbe's electrolysis of 2,3-butanedicarboxylic acid (succinic acid). Turns out, this compound is not very well researched in particular, and shows few ...
2 votes
0 answers
609 views

Is hydroxylamine monodentate or ambidentate ligand?

What is the total number of geometric isomers of the complex $\ce{[Pt(Cl)(py)(NH3)(NH2OH)]+}$? If $\ce{NH2OH}$ acts as an ambidentate ligand, then there should be six geometric isomers. Or is it ...
-1 votes
1 answer
77 views

Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles? [closed]

Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles(like 360°); as there won't be any deflection in the analyser of the polarimeter?
-1 votes
1 answer
297 views

Does no optical rotation always implies optical inactivity? [duplicate]

This question popped up in my mind in reference to this question, Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles? Suppose that I give a chemistry ...
1 vote
1 answer
460 views

Does the 3D structure generated with MolView violate the wedge-dash rules of "above/below the plane"?

I've been taught that in a wedge-dash diagram, the wedge represents a bond above the plane of the paper, and the dash represents a bond below the plane. Accordingly, I expected the structure of this ...
3 votes
2 answers
3k 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 votes
3 answers
3k views

Why is diequatorial trans-1,2-dimethylcyclohexane more stable than diaxial trans-1,2-dimethylcyclohexane?

Consider diequatorial trans-1,2-dimethylcyclohexane and diaxial trans-1,2-dimethylcyclohexane as shown in the figure below [1, p. 178]. In both compounds, the ring is free of angle strain. trans-1,2-...
70 votes
4 answers
28k views

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

In the highly-rated TV series, Breaking Bad, Walter White, a high school chemistry teacher recently diagnosed with cancer, takes to making the illicit drug, crystal meth (methamphetamine), by two main ...
2 votes
1 answer
623 views

How does Entropy influence the racemization of an optically active compound?

We were doing the topic "Isomerism" in our Organic Chem class and there's a question in our worksheet whose answer I haven't really understood, the question is as follows: The racemization ...
8 votes
2 answers
617 views

Stereochemistry of nitrosyl chloride addition to an alkene

My book states addition of $\ce{NOCl}$ to propylene results in 2‐chloro‐1‐nitrosopropane: Would it follow syn or anti addition? According to Mallya and Nagendrappa [1], the reaction would follow syn ...
1 vote
0 answers
295 views

Monochlorination of (R)-2-chlorohexane: Number of possible chiral dichloro products

How many possible chiral dichloro products can be formed when (R)-2-chlorohexane reacted with one equivelent of $\ce{Cl2}$ in the presence of UV radiation (monochlorination only)? $$\ce{C6H11Cl + Cl2 -...
8 votes
2 answers
10k views

Optical isomerism in Co-ordination Compounds

Optical isomerism in normal organic molecules can be found out by looking for chiral carbon, and the number of isomers can be found out by drawing different spacial orientations of the same. But, I ...
4 votes
0 answers
265 views

Is There a Problem with the Assignment of Stereochemical Descriptors by ChemDraw in Select Examples?

While using ChemDraw Professional 21.0.0.28 to construct some cyclic allenes and rotationally restricted biphenyls, I came across anomalous assignments of stereochemistry. [For the latest version of ...
2 votes
2 answers
582 views

Reactivity of 1-bromo-4-tert-butylcyclohexane isomers with methanol

(1s,4s)-1-bromo-4-tert-butylcyclohexane (1) and (1r,4r)-1-bromo-4-tert-butylcyclohexane (2) are heated (E2) with $\ce{NaOCH3}/\ce{CH3OH}.$ Which isomer will react faster? What will change when $\ce{...
-1 votes
1 answer
162 views

Why is the 'side' of a double bond defined across the double bond horizontally rather than vertically? [closed]

When we are determining cis-trans isomerism, we seem to refer to a molecule's 'side' in relation to the double bond in a horizontal manner, as if we had drawn a mirror line through it horizontally. ...
34 votes
3 answers
3k views

Why is 1-ethylidene-4-methylcyclohexane chiral?

As far as I can tell, there doesn't seem to be a chiral carbon in the compound, 1-ethylidene-4-methylcyclohexane. The C-4 of the cyclohexane ring has two groups with exactly the same connectivity, and ...
5 votes
1 answer
1k views

Why 5-member rings prefer being cis-fused?

It always bothers me how whenever I am doing practice problems I never got a proper explanation as to why 5-member rings prefer(thermodynamically) being cis- rather than trans-fused( as opposed to ...
1 vote
0 answers
42 views

How does the size of a molecule subject to photo-isomerization affect it's isometric configuration?

When azobenzene is photo-excited to a higher energy configuration, the electron orbital take new energy levels and position's, changing the over all configuration of the molecule. Now, if various ...
5 votes
1 answer
17k views

How to draw Fischer projections for carbon chain having more than two carbons?

How can we draw Fischer projections for one-five carbon compounds? For example, say we have pentane-2,3,4-triol ($\ce{CH3-CHOH-CHOH-CHOH-CH3}$; image below). With wedge and dash structure, the ...
1 vote
1 answer
2k views

How many dichlorinated products including stereoisomers can be isolated when (S)-2-chlorobutane reacts with Cl2 /hv?

This is my attempt at solving this problem. I get 6 products. However my book says the answer is 5 products.
13 votes
1 answer
3k views

R/S configuration of bridging carbon in bicyclic system

I am trying to figure out the R and S configuration of bridging carbons in bicyclic systems. In the image, there are two bicyclic systems and depending on the position of the Br substituent, the R or ...
3 votes
1 answer
195 views

X-ray structure analysis mirrored coordinates?

How to ensure, that X-ray crystallography structure analysis was done right to provide correct, non-mirrored atomic coordinates? Example: Following Wikipedia image, is generated from data taken from ...
1 vote
0 answers
44 views

When does the Mukaiyama-Addition follow which transition state and how does it affect the stereochemistry?

in the course on enantioselective organocatalysis, we discussed the route to hexoses via organocatalytic aldol addition and subsequent Mukaiyama addition. The use of either TiCl4 or MgBr2 leads to ...
3 votes
2 answers
2k views

How can I find all possible isomers of a given molecule?

I attend a course on combinatorics (mathematics) which contains many examples related to chemistry. Unfortunately, I don't have enough chemistry knowledge to feel comfortable with the examples. For ...
4 votes
2 answers
10k views

Pseudo chiral centre

I was reading about stereoisomers and I came across a term pseudo chiral centre. I looked up on the net for its definition and found a weird formula for calculating no. of isomers if the compound has ...
8 votes
2 answers
646 views

Identification of endo and exo products in this Diels-Alder reaction

This synthesis example is shown in the book Cycloaddition Reactions in Organic Synthesis by S. Kobayashi and K. A. Jorgensen (link), on p. 15: 8 is a chiral catalyst, which can be ignored, in the ...
0 votes
0 answers
38 views

What is the difference between Cholestanol 5alpha and 5beta?

What is the isomeric relation between 5Alpha Cholestanol and 5Beta Cholestanol. I know that those forms appear after Hydrogenation of Cholesterol but unfortunately I cannot find any article or ...
2 votes
1 answer
240 views

Is it correct to class these two compounds as enantiomers?

This question is from GRB Problems In Organic Chemistry For Jee Advanced. Identify the relation between these two compounds: (a) Homomers (b) Enantiomers (c) Diastereomers (d) Different compounds ...
2 votes
1 answer
880 views

Number of chiral centers in Proline

I think it's two, but I am not able to access/find any information on the net that supports my claim or justifies why it's wrong. One chiral center is the obvious carbon attached to $\text{-(COOH)}$ ...
2 votes
0 answers
115 views

Can endo and exo products occur when the diene is not cyclic?

I have always thought that the diene needs to be cyclic for there to be endo and exo products. Perhaps, I formed this impression because most textbook examples that are used to illustrate the concept ...
3 votes
1 answer
2k views

Why is 1,3-dimethyl-cyclohexane a meso compound?

So i was trying to find the plane of symmetry in 1,3-dimethyl-cyclohexane in chair conformation, but then i realised the plane is present only at a particular orientation [see figure]. So why do we ...
12 votes
1 answer
4k views

Total number of stereoisomers of cyclobutane-1,2,3,4-tetracarboxylic acid

Question Find all stereoisomers of: My attempt I got four isomers, and none of them seem to be optically active as they either have a plane of symmetry or a point of symmetry: However, my sir keeps ...
0 votes
1 answer
104 views

Racemization on nucleophilic substitution by OH- ion [closed]

Here's the question I'm stumped by - According to the answer key, i) is the answer but why can't it be iv)? There is a chiral carbon in compound c) CH3(C2H5)CHCH2Br , so why won't the product (2-...
0 votes
1 answer
2k views

Difference between threo/erythro and cis/trans nomenclature

According to what I have read, it seems that erythro isomers are defined in the same way as cis isomers and same holds true for threo and trans isomers. Is there any difference between these two set ...
2 votes
1 answer
88 views

Relationship between the principal axes of inertia of an enantiomeric pair

If an object is chiral, its mirror image and itself are non-superimposable and represent two distinct versions of the same object. A hand, for instance, can be either the right hand or the left hand. ...
0 votes
2 answers
481 views

Hydrogens of cyclohexanol are enantiotopic or diastereotopic, which is true?

I am studying spin-spin coupling theory in NMR. Below is an exercise from Mcmurry's organic chemistry. The textbook says that * stands for chiral center. But is it true? When I searched for it some ...
2 votes
1 answer
838 views

How many stereoisomers can exist for 4,5-bis(3-hydroxyoct-1-en-1-yl)cyclopentane-1,3-diol?

Q.10 For the given compound $\ce{X}$, the total number of optically active stereoisomers is ____. This is from JEE Advanced 2018 second question paper. I thought the answer to be at least 32 because ...
-1 votes
1 answer
94 views

Why this structure is diastereomers instead of enantiomers

In this diagram optical isomers has divided in to 2 categories, one is diastereomers and enantiomers. Is the example for diastereomers correct? For me its looks like enantiomers
0 votes
1 answer
102 views

Racemization of hydrocarbon in presence of AlCl3

Our textbook mentioned that the compound in the diagram racemizes in presence of $\ce{AlCl3}$, but it didn't explain anything. Any help regarding the mechanism of the reaction would be appreciated.
1 vote
1 answer
120 views

Natural Sources for S-(-)-Limonene?

I'm interested in developing an undergrad organic lab that delves deeper into distillation/extraction, optical rotation and enantiomers. Our lab currently does a steam distillation extracting R-(+)-...
2 votes
1 answer
190 views

Posible Pair of Enantiomers

What is the number of possible enantiomers in monochlorination of 2-methybutane? My approach When $\ce{Cl2}$ is added to any alkane it prefers $3^\circ > 2^\circ > 1^\circ$. When it is being ...
13 votes
3 answers
28k views

Difference between Epimers and Diastereomers

My lecture notes describe epimers as compounds which differ by configuration at only one carbon and gives the example of D-erythrose and D-threose as being epimers. However isn't that the same thing ...
0 votes
0 answers
34 views

How are these two enantiomers? [duplicate]

I was wondering how these two chair conformations are enantiomers, because they do not seem to be mirror images of each other. The molecule on the left undergoes a ring flip to achieve the ...
7 votes
1 answer
3k views

In the Haworth projections of D and L glucose, is the stereochemistry at every carbon except the anomeric carbon just inverted?

I'm having a bit of trouble grasping sugar stereochemistry. Using glucose as an example, if you cyclize D and L glucose, is the stereochemistry at every carbon just inverted from the other form? ...
0 votes
1 answer
4k views

Polarity and stability

Why is cis-1,2-cyclohexadiol less polar than trans-1,2-cyclohexadiol? I know it has something to do with stability and chair conformations, but I'm not sure how it relates to polarity. I know cis-1,...
0 votes
0 answers
215 views

Why is C-S-C bond angle in thiirane so small at 48.5 degrees?

Why is the C-S-C bond angle in thiirane (48.5 degrees) so much smaller than C-O-C bond angle in oxirane/epoxide (60 degrees). Source: https://coek.info/pdf-three-membered-ring-heterocycles-.html
5 votes
2 answers
1k views

Cahn–Ingold–Prelog Rules, cyclic structures, and breaking ties

(3S,5R)-3-ethyl-5-methylcyclohex-1-ene Does anyone know how one reaches the conclusion that the 5C is R? I tried using the Cahn–Ingold–Prelog priority rules but kept getting confused. From chem....
-4 votes
1 answer
122 views

Why total stereoisomers is 1 even if no geometrical isomers and optical-isomers are present [closed]

Let's for example take the complex structure type $\ce{MA_6}$, What will be the Total number of Stereo-isomers (=[Geometrical-isomers]+[optical-isomers]). My effort was that There will be no G.I and ...
1 vote
0 answers
1k views

Total number of Isomers of [Co(NH3)5(NO2)](NO3)2 [closed]

I encountered this question in my country's Chemistry textbook of class 12. No solutions are published, but the answer given at the back states - "There are 10 possible isomers. (Hint: There are ...
0 votes
1 answer
580 views

Is a tetrahedral complex with two symmetric bidentate ligands optically active?

If the shape of of a complex $\ce{M(AA)2}$ (with $\ce{AA}$, a bidentate ligand) is tetrahedral, then is it optically active? Currently I know that it is optically inactive, but I want to know the ...

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