Isomers which can be interconverted by rotation around a single bond. These typically have a very low energy barrier to interconversion.

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Hydrogen bonding in eclipsed conformations vs gauche

Last semester in organic chemistry 1, we learned that gauche conformations have lower energy/higher stability. However, my thought is that if you have interacting OH groups, the hydrogen bonding ...
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1answer
148 views

Energy profile of cyclohexene conformations

The energy profile for cyclohexane flipping looks like this: How does the corresponding diagram for cyclohexene look like?
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197 views

Conformation of six-membered ring constituting a bridged compound

What is the conformation of the cyclohexane ring constituting [2.2.1]-bicycloheptane? Is it boat or twisted boat? Is that conformation abundant in other bicyclic systems containing a cyclohexane ...
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2answers
156 views

Factors that affect Diels-Alder reaction rate

As for factors that affect the rate of the Diels Alder reaction, having an s-cis conformation is primary. But in a case as shown below, what makes the second diene react faster compared to the third? ...
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2answers
197 views

Why is the eclipsed conformer more stable than the bisected conformer in 1-butene?

I have just started learning conformational analysis, and a major doubt came into my mind. In simple alkanes such as ethane, the staggered conformer is much more stable than the eclipsed conformer. ...
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1answer
75 views

Question based on energy of conformations of ethane and propane

Q)which points on the given energy diagram represents eclipsed confirmation of ethane and staggered confirmation of propane respectively? Attempt: Eclipsed configuration is unstable because of ...
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1answer
377 views

Does trans 1,3-dichlorocyclobutane have zero dipole moment?

Does this compound have zero dipole moment? I think it has a non-zero dipole moment. If I assume the ring to be planar, then the dipole moments of each $\ce{C-Cl}$ bond cancel out. (One is upward ...
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1answer
263 views

How can the gauche-effect be explained?

Generally, anti-conformations are more stable. But in the case of 2-fluoroethanol, the gauche confirmation is more stable. It's given in March's advanced organic chemistry book that intramolecular ...
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91 views

Torsional energy diagram for toluene

Exercise: Sketch a complete (360 degree) torsional itinerary for toluene. My take: Well it's only for 300 degrees - the pattern continues by one hill more. Energy (strain) is plotted on the ...
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1answer
44 views

Conformation identifying cis and trans

How to identify cis and trans in conformers of cyclo hexane.i know that there are two positions axial and equatorial but using this data how to identify cis or trans? Also why are functional groups in ...
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1answer
5k views

What is the difference between steric strain and torsional strain?

I know that in ethane, the extra energy present in the eclipsed conformer is caused by torsional strain. In butane, the gauche conformation experiences steric strain. But the eclipsed conformation ...
18
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1answer
632 views

When can a molecule be considered freely rotating at room temperature?

This question sparked from a long discussion in chat about the nature of $\ce{H2O2}$ and whether that molecule can be considered to rotate around the $\ce{O-O}$ axis (and hence display axial ...
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1answer
188 views

Most stable conformation of aldehydes and ketones

Why is the most favorable conformation of ketones and aldehydes the one where the alkyl group is anti to the other alkyl group (or hydrogen atom in an aldehyde) as attached? Why isn't more stable the ...
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1answer
157 views

Calculation of the lowest energy conformation with a webbased solution or freeware

I like to draw a molecule in different conformations in a) website or b) freeware and Calculate its relative energy difference (for example to the lowest global energy conformation) Display the ...
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3answers
571 views

Is there a definition of rotatable bond?

Some intramolecular bonds are rotatable in the sense that the torsion angle around this bond is flexible (for example, $\psi$ and $\phi$ angles in a protein backbone). Others are essentially fixed ...
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1answer
175 views

Trying to understand SMILES(?) patterns

In the example calculation from the conformer search package fafoom is a mysterious pattern that I'd like to understand. The SMILES code of the given example structure is: ...
5
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1answer
101 views

Determining chirality after considering conformational interconversion in a cyclohexane

Basically I want to know what does the question mean when it says "taking into consideration conformational interconversions." I assume it means, when I draw the mirror image of the given compound, ...
6
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0answers
138 views

How big is the gauche interaction of methyl with phenyl in a disubstituted cyclohexane?

I'd like to compare the equatorial 1-Methyl-2-phenyl-cyclohexane conformation of with axial conformation of 1-Methyl-3-chloro-cyclohexane conformation. In which molecule there is less steric ...
4
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1answer
132 views

Is there an A value for the carbaldehyde and vinyl groups?

A methylene ($\ce{=CH_2}$) group ist sterically less hindered than a methyl ($\ce{CH_3}$) group. I'm wondering if the carbonyl ($\ce{C=O}$) group is sterically more or less larger than a methylene ...
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1answer
86 views

Carbohydrate conformations

I have to questions regarding the conformations of carbohydrates. There are 38 different conformations for an aldohexose or ketohexose, including $\alpha$ and $\beta$ anomers, namely 2 chairs, 6 ...
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1answer
169 views

How can rotamers of alpha-keto esters be named to distinguish between different geometries?

When talking about free rotation it is often helpful to determine about which geometric arrangement one is referring to. For example in the case of butane we talk about several eclipsed or staggered ...
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0answers
76 views

Which of the five conformers of propyl propanoate is most stable?

I've worked out five different conformations of propyl propanoate: I think the bisected conformations (E) should be the most stable one. Are my rationals & suggestions in my scheme correct?
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1answer
529 views

Conformations of Cyclohexane

Is there any such thing as a twist chair conformation? Also, the boat and the chair conformations are achiral, while the twist boat conformation of cyclohexane is chiral and dissymetric. What about ...
7
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1answer
175 views

Why do sp2 carbons tend to prefer eclipsed conformations whereas sp3 carbons prefer staggered

I am a second year undergraduate and have come across this when studying stereochemistry and conformations and have been unable to find a satisfactory answer. I know that $\ce{sp^3}$ carbons prefer ...
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1answer
204 views

What is torsional strain?

I am having difficulty in understanding the concept of torsional strain. Can someone explain it to me in a more elaborate manner? I mean why should bond restrict movement in eclipsed conformation? ...
5
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1answer
67 views

Energy of Eclipsed Interactions

I am asked to identify the highest and lowest energy conformations for the following bond-line structure (I think it is 2,2-dimethylbutane). I drew a Newman projection (for all 6 conformations) and ...
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52 views

Ground state conformation of dimethyl disulfide

What is the ground state conformation of dimethyl disulfide ? The two which seem reasonable to me are trans to avoid methyl-methyl gauche interactions or gauche due to sulfur donation into the S-Me ...
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1answer
1k views

Number of gauche interactions in an alkane

The textbook states that (a) has 2 gauche interactions, (b) has 3 gauche interactions and (c) has 3 interactions. But how do we determine this? I thought a gauche interaction would occur when two ...
3
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1answer
608 views

Assign the configurations of the stereo centres in (-)-menthol and (+)-neomenthol?

I have to assign R or S to the chiral centers in (-)-menthol and (+)-neomenthol. The results I got are shown below in the picture. However, when I looked on Wikipedia to check my answers they ...
4
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1answer
265 views

Conformational analysis determining forces

So the determining forces in the conformational analysis (what will be the more stable state and what will be the more excited state) according to my textbook are: Steric interaction Electron ...
4
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1answer
145 views

IBrF2 - van der Waals repulsions - and number of unique bond angles

I understand that the molecule $\ce{IBrF2}$ is T-shaped, with three ligand atoms and two non-bonding pairs. However, how many unique bond angles can this molecule exhibit? My professor argues for ...
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1answer
1k views

Energy Diagram for Propane

I've been unable to find an energy diagram for propane either in my book or online via Google. So I resorted to making my own. I suspect that propane isn't covered because it's essentially the same ...
3
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2answers
252 views

Conformations of butane

Would these be valid conformations of butane? I tried matching these up with the group but my drawings all seem rotated versus the book. I'm fairly sure my anti conformer is correct, along with my ...
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1answer
363 views

Conversion of s-trans butadiene to s-cis butadiene

No nodes should be introduced in the rotational interconversion between the s-trans and s-cis forms of 1,3-butadiene. What is the explanation for that, if one of the $\pi$-systems should rotate ...
4
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1answer
136 views

How to calculate the frequency of cyclohexane conformational interconversion?

My book mentioned that the energy barrier for cyclohexane to reach the half-chair conformation is 50.6 $\text{kJ mol}^{-1}$. It says that from this value, it was calculated that cyclohexane undergoes ...
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2answers
319 views

Why is this chair conformation the most stable and which leaving group is best?

I'm confused about how this chair conformation was constructed and why that particular Cl leaves. Why is one of the Cl's drawn axial while the others are drawn equatorial (it seems like the others ...
8
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1answer
454 views

Covalent bond deformation

When do covalent bonds of a molecule $M$ extend or compress while no bonds in $M$ are broken? I can conceive of some possibilities but I don't know how common they are: Temperature changes ...
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3answers
754 views

Which is most stable conformation of optically inactive butane-2,3-diol?

The most stable conformation of optically inactive butane-2,3-diol is: (A)  (B)  (C)  (D) I chose C as the correct answer but, in the answer key it is given to be B. C is the ...
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1answer
1k views

Solvation effect on cyclohexane

I ran molecular dynamics simulation with a molecule of methylcyclohexane soaked into a water box. On the other hand I ran Monte Carlo with the molecule alone (no soaking). I performed this for the ...
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1answer
303 views

Methylcyclohexane chair conformers

I am trying to create the molecule of the methylcyclohexane in the equatorial and axial conformers. I read in this site about the chair conformation. My molecule looks like the following picture ...
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1answer
260 views

Percentage of a conformer in vacuum

I just started with Molecular dynamics simulations. My background is computer science but I'm learning about scientific computing and thus my jump into MD. Having said that, I was asked to calculate ...
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3answers
4k views

Which conformer of Beta D-glucose is more stable

I drew the two chair conformers of Beta D-glucose: Which one is more stable? I think it's the one with all of the OH groups in the equatorial position because of less steric hindrance, but I also ...
7
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1answer
169 views

Rotation energy barrier for carboxypyrazolate

In this molecule, which is 3,5-dimethyl-4-carboxypyrazolate (unless I got it wrong): I do not think there is free rotation around the bond indicated in red, because one can write a resonance ...
6
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1answer
735 views

Effect of periodic acid on cyclohexane derivatives

Periodic acid (per-iodic acid, $\ce{HIO4}$ ) cleaves vicinal diols(to carbonyls) via a cyclic intermediate. Due to the cyclic intermediate, it needs a syn configuration for the $\ce{-OH}$ groups for ...