Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
4
votes
0answers
37 views
Endo/Exo for same length bridges
I'm looking at a cycloaddition that produces a bicyclic intermediate, there are two different ways of doing the addition which can be described as endo/exo. However, all three bridges are the same ...
0
votes
0answers
26 views
Do grignard mechanisms produce isomers?
When I attempted this question I got an S configuration, while the answer shows an R configuration. I am thinking that this reaction would produce an enantiomer but I was taught that this mechanism is ...
1
vote
0answers
28 views
Enantioselective alkylation of Aldehydes by Dialkylzinc reagents
Enantioselective catalysis is one of the important reactions in Organic chemistry which has huge applications in practical basis for synthesis of optically pure natural compounds. In this respect, I ...
4
votes
1answer
65 views
Optical Isomerism in Coordination Compounds of type MA₂B₂(CC)
I was asked the following question:
How many optical isomers are there for $\ce{[Cr(NH3)2Cl2(en)]^+}$ ?
First of all I figured out the following four geometrical isomers of the above complex:
Out ...
-1
votes
2answers
34 views
Is there absolotely no relation between R/S configurations and d/l optical rotations?
Is there such a relation between R/S configurations and d/l optical rotation that, if we experimentally know that R configuration of a fixed compound gives 'l' rotation then can we infer that the S ...
-1
votes
1answer
30 views
Enantiomers and couple of enantiomers
I ask myself a question for some time but it's impossible to me to find the answer!
I can't understand the difference when we say " that molecule has a enantiomer " and when we say " has a couple of ...
3
votes
0answers
126 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 ...
4
votes
3answers
89 views
Is there a thermodynamic driving force for racemisation?
Why does racemisation occur?
My doubts are:
Is it due to entropy?
If it is due to entropy, how is the reduction of optical activity by racemisation a consequence of increased thermodynamic ...
0
votes
1answer
31 views
What is the configuration of dimethyl[tris(trifluoromethyl)]-λ⁵-phosphane?
I know that $\ce{(CH3)2P(CF3)3}$ is geometry of trigonal bipyramid and according to Bent's rule $\ce{CH3}$ goes to axial positions and $\ce{CF3}$s remains on equatorial positions. However, as per ...
4
votes
2answers
96 views
Does 3,6-di-X-cyclohexa-1,4-diene have stereo centers?
The following question has multiple correct answers:
The book out of which the question is taken shows that a, b and d are correct answers.
According to me c should also be correct, as it shows ...
1
vote
2answers
34 views
Are the stereoisomers of nucleosides actually anomers?
An anomer is an epimer at an (hemi)-acetal carbon like $\ce{R2C(OR')2}$.
Why is the 1'-position of a nucleoside referred to as the anomeric center despite the lack of acetal functional groups?
0
votes
1answer
25 views
According to the Cahn-Ingold-Prelog system assign a priority to each of the following groups. (Highest priority is 1) [closed]
1-CH(CH3)CH2F
2-CHCl2
3-CH2Br
4-C(CH3)3
this is the order i did using the system but i am having a hard time understanding it and was wondering if anyone could tell me if my answer is correct, and if ...
1
vote
1answer
47 views
Classification in Stereoisomerism [closed]
I was trying to understand stereoisomerism. I am having trouble creating a 'flow chart' of Stereoisomerism. While there are many sources available over the internet and books, I don't find a standard ...
5
votes
0answers
76 views
What compound has the strongest optical rotation of polarised light?
A question recently asked here whether compounds know to be chiral can have non-measurable optical rotations: Are there chiral compounds that don't rotate plane-polarized light?.
Apparently they ...
6
votes
1answer
421 views
Are there chiral compounds that don't rotate plane-polarized light?
I know that meso compounds have chiral centers but don't rotate plane-polarized light, and I know that there can be non-traditionally chiral compounds (e.g. ones with large substituents that prohibit ...
3
votes
1answer
55 views
Assign stereodiscriptor to 4th carbon of 3-ethyl-2,4-dimethly-5-(propan-2-yl)heptane-1,7-diol
Here is the molecule. Clearly the 4th carbon is chiral. I have drawn the diagraph for it, but the exploratory pathways of the left and right chains are the same. So, the problem is that the two chains ...
0
votes
2answers
104 views
Why does 1,3-dichloropropane not show stereoisomerism?
It is a multiple choice question:
Which compound does not show stereoisomerism?
A 1,2-dichloroprop-1-ene
B 1,2-dichloropropane
C 1,3-dichloroprop-1-ene
D 1,3-dichloropropane
I ...
-1
votes
1answer
125 views
Determining R and S configuration for a cyclic compound when the lowest priority group is on the plane of the paper
I am struggling with determining R and S configuration for the following compound
I know how to give R and S configuration for a cyclic compound like the compound above if the lowest priority group ...
0
votes
2answers
112 views
What is the most stable conformation (Newman Projection) of CF3CH3?
Is a totally eclipsed Newman projection the most stable conformation for a 2 carbon compound, with one carbone bonded to more electronegative atoms (making them partial negative), and the other carbon ...
0
votes
0answers
28 views
Can the CDK represent a mixture of stereoisomers
Biovia (previously MDL) Enhanced Stereochemical Representation enabled specifying mixtures of enantomiers by annotating sterocenters with a group and one of these types:
ABSOLUTE:
Stereogenic ...
1
vote
0answers
24 views
Why atropisomers are called conformers?
Changing one atropisomer to another requires bond breaking (in some cases the removal and reattachement of steric groups, according to my understanding) so how it is possible that according to IUPAC ...
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votes
1answer
33 views
what is superimposability of mirror images of this molecule? [closed]
I don't get why (a) and (d) are achiral when we cant superimpose their respective mirror images?Or can we superimpose them?
0
votes
2answers
160 views
Fischer projections
Can somebody tell me how why they changed/choose the groups for vertical and horizontal lines. As far as I know the vertical lines represent group going away from us and horizontal depicts coming ...
0
votes
0answers
61 views
Interpreting wedge dash
What does wedge-dash in this structure diagram of 2'-methoxy-6-nitro[1,1'-biphenyl]-2-carboxylic acid mean? Both the structures are perpendicular to each other, so why is wedge dash shown on front ...
0
votes
0answers
37 views
R/S descriptors in long carbon chain
I'm trying to figure out how to assign R/S descriptors using a Fischer model without transforming it into a spacial one.
What I learned so far is the method to assign it for 'terminal' (I'm gonna use ...
2
votes
2answers
186 views
Stability of geometrical isomers in cycloalkanes
Among the following, which should be the most stable compound?
1)Cis-cyclohexane-1,2-diol
2)Trans-cyclohexane-1,2-diol
3)Cis-cyclohexane-1,3-diol
4)Trans-cyclohexane-1,3-diol
My thought process is-...
1
vote
0answers
38 views
Which of the following molecules are enantiomers? [closed]
My book says that only molecule 7 is enantiomer of molecule 1. Why is this? Why can't molecule 1 and 2 be enantiomers?
1
vote
1answer
67 views
Are Anomers Epimers?
epimers are the class of stereoisomers which differ along configuration at any carbon in a carbohydrate(generally),
And anomers are the kind of stereo isomers that differ at the carbonylic carbon, ...
2
votes
1answer
159 views
2
votes
2answers
111 views
Can chiral atoms have same substituents but with different orientations?
So consider this molecule. We have to determine whether nitrogen atom is chiral or not.
MY IDEAS:
Now going by all I have read, for chiral atoms only criteria is substituents to be different. Here ...
10
votes
5answers
1k views
If a chiral molecule reacts with an achiral molecule will the product be chiral or achiral?
My book says that a pair of enantiomers will react the same way with an achiral substance.
How is this possible? Does this imply that the product is achiral, even though the enantiomers are chiral? ...
7
votes
2answers
141 views
Number of spatial arrangements of tetrasubstituted biphenyl
According to my book 2-bromo-2'-(1-chloroethyl)-6'-iodo-6-(prop-1-en-1-yl)-1,1'-biphenyl has eight possible spatial arrangements. How can this be so? I can think of only four – left two groups being ...
2
votes
1answer
148 views
Cahn–Ingold–Prelog priority of CN vs CH2NH2
Why does $\ce{CH2NH2}$ have lower priority than $\ce{CN}$? The carbon on the first molecule is bonded to (N,H,H) while the carbon on the second molecule is just bonded to (N). I can't seem to find ...
0
votes
0answers
39 views
What compounds give two products on reacting with NH2OH?
This is a question from the chapter stereochemistry of my coaching module. The answer options include CH3CHO, DCHO, etc. How do I do this? I have an idea that if we take a racemic mixture of D and L ...
6
votes
2answers
467 views
Do you assume undrawn hydrogens are pointing away from you when determining R/S?
When determining R/S of stereoisomers, the group with the smallest atomic number needs to be in the back (dashed line). But if no group attached to a chiral center is drawn in dashed line, do we ...
-1
votes
1answer
79 views
Twisting stereoisomers with rings to determine R/S [closed]
I know that if the smallest atomic number group is not in the back, we can twist the molecule so that it is in the back and then determine if it is R/S (Left image). But if the chiral center is ...
-1
votes
1answer
68 views
Stereogenic Center Question
In cholesterol, I don't understand why the two points I circled are stereogenic centers. Isn't the left carbon attached to an OH, H, CH2, and CH2? And isn't the right carbon attached to CH, CH2, CH, ...
-1
votes
1answer
428 views
Explain optical activity in Biphenyl compounds
How is optical activity explained in biphenyl compounds using atropisomerism.
NOTE: I was taught that if vertical symmetry exists then optical activity is not shown by any substituted biphenyl ...
1
vote
1answer
293 views
H-NMR Equivalent Protons and Coupling of Glycerol
I've been searching for explanations to understand why the labeled protons on carbons 1 and 3 are not equivalent in the below figure.
Another figure that shows the same results:
SDBS confirms the ...
0
votes
1answer
87 views
Systematic Approach to Finding Number of Isomers [duplicate]
I have this compound
I want to know how many isomers (including stereoisomers) may have this constitution. Is there a systematic approach towards solving such types of problems related to the total ...
0
votes
0answers
57 views
How many stereoisomers can exist for 4,5-bis(3-hydroxyoct-1-en-1-yl)cyclopentane-1,3-diol?
This is from this year's JEE Advanced question paper.
I thought the answer to be atleast 32 because of exactly 5 stereocentres present. One of the double bond cannot show geometrical isomerism ...
0
votes
2answers
122 views
Meso and achiral does both term means the same?
When a molecule has plane of symmetry, or centre of symmetry it is termed as an achiral compound (though it contain some chiral centres). Same goes for the meso compounds due to the internal ...
2
votes
0answers
73 views
Dextro or laevo-rotatory compound conversion [closed]
Will applying an external electric field to a racemic mixture will convert the optically active compound(mixture of both Dextro and laevo-rotatory) into a particular dextro or laevo-rotatory compound?
...
3
votes
1answer
54 views
Under what circumstances can the stereochemistry at nitrogen atom be faithfully retained and identified?
Under what circumstances can the stereochemistry at nitrogen atom be faithfully retained and identified?
Because in most cases nitrogen atoms tend to undergo stereorandomisation by flipping due to ...
0
votes
1answer
181 views
1,4-diphenyl-1,3-butadiene (E,E) and (E,Z) Isomer Newman Projections
I was wondering if it is possible to draw the Newman projections of the (E,E) and (E,Z) isomers of 1,4-diphenyl-1,3-butadiene in the following manner that I have? I wasn't quite sure about how to ...
3
votes
1answer
404 views
How to calculate the percentage yield for enantiomers in free radical halogenation?
How many mono-chlorinated products of 2-methyl butane will be formed upon chlorination in the presence of sunlight?
Find the percentage of major product formed.
Six products were formed: two ...
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votes
1answer
102 views
Number of total stereoisomers of a piperazine derivative
How do I find out the total number of stereoisomers of 3,6-dimethylpiperazine-2,5-dione?
As far as I can see, the compound has two chiral carbons. Would the nitrogens make a difference? They seem ...
2
votes
0answers
93 views
Does dihydroimidazole show geometrical isomerism?
Does dihydroimidazole (above) exhibit geometrical isomerism? Does the fact that the lone pair is involved in conjugation with a double bond affect anything?
As far as I know, it does not exhibit ...
13
votes
2answers
738 views
Number of stereoisomers of tetramethylspirononane
The above compound – 2,3,7,8-tetramethylspiro[4.4]nonane – clearly exhibits both optical and geometrical isomerism. The question is, how many stereoisomers does it have in all?
As the number of ...
2
votes
0answers
106 views
How to find the number of optically active and optically inactive isomers for a spiropentane derivative? [duplicate]
What will be the number of optically active and inactive isomers 1,2,4,5-tetramethylspiro[2.2]pentane?
The question asked for the difference between number of optically active and optically inactive ...
