Why is the chair conformation the most stable?

Asked By: Hermenegil Nerenberg | Last Updated: 23rd January, 2020
Category: science chemistry
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The chair conformation is more stable because it does not have any steric hindrance or steric repulsion between the hydrogen bonds. Of these two positions of the H's, the equitorial form will be the most stable because the hydrogen atoms, or perhaps the other substituents, will not be touching each other.

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Consequently, which conformation is more stable?

In terms of stability, the staggered conformation is more stable than the eclipses. This is for two reasons: 1) Steric hindrance. In the eclipsed conformation, the positioning of the atoms forces them closer together, increasing the amount of steric strain in the molecule.

Similarly, which chair is more stable? The chair conformation is the most stable conformation of cyclohexane. A second, much less stable conformer is the boat conformation. This too is almost free of angle strain, but in contrast has torsional strain associated with eclipsed bonds at the four of the C atoms that form the side of the boat.

Likewise, people ask, why is the chair conformation more stable than the boat?

Chair conformation of cyclohexane is more stable than boat form because in chair conformaion the C-H bonds are equally axial and equatorial, i.e., out of twelve C-H bonds, six are axial and six are equatorial and each carbon has one axial and one equatorial C-H bond.

Why is Equatorial more stable?

When substituents are in the equatorial position, they are farther away from each other. This increases the stability of the conformation. In the pictures below, the methyl in the equatorial position is more stable because it avoids interaction with the hydrogen atoms.

39 Related Question Answers Found

Why is half chair so unstable?

The half chair form is least stable due to maximum strain. Due to interaction between two flagpole hydrogens, there is steric strain in boat form and also torsional strain is present. It is 6.5kcal/mol less stable than the chair form.

Which is more stable gauche or eclipsed?

The gauche form is less stable than the anti form due to steric hindrance between the two methyl groups but still is more stable than the eclipsed formations. Such an interaction is often referred to as a gauche-butane interaction because butane is the first alkane discovered to exhibit such an effect.

What is the energy difference between the eclipsed conformations?

The energy of the eclipsed conformation is approximately 3 kcal/mol (12 kJ/mol) higher than that of the staggered conformation. Torsional strain (or eclipsing strain) is the name give to the energy difference caused by the increased electrostatic repulsion of eclipsing bonds.

Which Stereoisomer is more stable?

A chair conformation is one of many conformations of a cyclohexane ring and it is most stable. It has equatorial and axial bonds. The equatorial bonds (e) are perpendicular to the axis of the ring, while axial bonds (a) are parallel to the axis of the ring.

What is the most stable Newman projection?

The most stable one would have the rear hydrogen in between the front methyl and bromine in a staggered conformation to minimize [lone-pair]-[bonding-electron] repulsions. 4) Rotate the rear groups on the C2−C3 bond 120∘ counterclockwise from the Newman projection shown, and you'll have it.

What is torsional strain?

Torsional strain or eclipsing strain is the increase in potential energy of a molecule due to repulsion between electrons in bonds that do not share an atom. eg: Consider two conformations of ethane: The smallest dihedral angle is 60º in 1; it is 0º in 2. Consequently, torsional strain is greater in 2 than in 1.

Which is the least stable cyclohexane conformation?

Boat conformation is the least stable, with the highest energy, has steric hindrance between the two equatorial hydrogens on carbon 1 and carbon 4, and has torsional tension because each bond almost completely ellipses other bonds in the Newman projection.

Are Cycloalkanes planar?

Planar cycloalkanes is a term that probably refers to cycloalkanes that can exist in a flat plane. An example of a planer alkane is cyclopropane, which consists of three carbons connected to each other. Other cycloalkanes can possess a multitude of conformations which may or may not be planar.

Why is the boat conformation less stable?

Close proximity of the flagpole hydrogens results in steric strain. Eclipsing of carbon-hydrogen bonds on adjacent carbon atoms (3) results in torsional strain. Consequently, the boat conformation of cyclohexane ring is less stable than the chair conformation.

Are chair conformations enantiomers?

The chair conformer of the cis 1,2-dichloro isomer is chiral. It exists as a 50:50 mixture of enantiomeric conformations, which interconvert so rapidly they cannot be resolved (ie. separated). Since the cis isomer has two centers of chirality (asymmetric carbons) and is optically inactive, it is a meso-compound.

Why is chair form preferred over boat form?

The chair conformation drawing is more favored than the boat because of the energy, the steric hindrance, and a new strain called the transannular strain. The boat conformation is not the favored conformation because it is less stable and has a steric repulsion between the two H's, shown with the pink curve.

Which is more stable cyclohexane or cyclopentane?

Cyclopentane is slightly more stable because it can relieve some of the bond strain by buckling the ring and pushing one carbon out of the plane. Cyclohexane has effectively zero strain, since all the carbons now have exactly the correct bond angle for optimum overlap of their orbitals with their neighbours.

Are wedges always axial?

If both substituents are on a wedge, then you can call them "up", and on those carbons you would draw them both "up". Up/down does not correlate to equitorial/axial. Check it out here. Both are on wedges, both are "up" then, and when drawing the chair conformation, one is axial and another equitorial.

What is the lowest energy conformation?

The lowest energy conformation of ethane, shown in the figure above, is called the 'staggered' conformation, in which all of the C-H bonds on the front carbon are positioned at dihedral angles of 60°relative to the C-H bonds on the back carbon.

Is lower energy more stable?

The lower the potential energy of the system, the more stable it is. Chemical processes usually occur because they are thermodynamically favourable. "Thermodynamically favourable" means from high energy to low energy, or, put another way, from less stable to more stable.

What is Newman projection formula?

Newman. projection. 3D structure. A Newman projection, useful in alkane stereochemistry, visualizes the conformation of a chemical bond from front to back, with the front atom represented by a dot and the back carbon as a circle. The front carbon atom is called proximal, while the back atom is called distal.