Gauche effect in 2-fluoroethanol

In summary, the conversation discusses the stability of anti confirmation and the gauche effect in 2-fluoro ethanol and 1,2-difluoroethanol. While anti confirmation is generally more stable, the gauche confirmation is more stable in these two compounds. The reason for this is not due to intramolecular Hydrogen bonding, as stated in March's advanced organic chemistry book, but rather due to hyperconjugation. However, the individual is struggling to understand this concept and is seeking clarification on the actual reason for the gauche effect.
  • #1
Titan97
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Generally, anti confirmation is more stable. But in case of 2-fluoro ethanol and 1,2-difluoroethanol the gauche confirmation is more stable.

It's given in March's advanced organic chemistry book that intramolecular Hydrogen bonding is not the correct reason for the stability. Wikipedia explains it using hyperconjugation, but I am not able to understand it. What is the actual reason for gauche effect?
 
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  • #2
In the gauche conformation, the CH and CF bonds are in anti-position. Hence you can draw a resonance structure H+ C=C F-. This is only possible if the two atoms are not perpendicular to the pi bonding plane.
 

FAQ: Gauche effect in 2-fluoroethanol

What is the Gauche effect in 2-fluoroethanol?

The Gauche effect refers to the preference of a molecule to adopt a specific conformation in which the largest groups are in a gauche (staggered) orientation with respect to each other. In the case of 2-fluoroethanol, this refers to the preference for the fluorine atom to be in a gauche position with respect to the hydroxyl group.

What causes the Gauche effect in 2-fluoroethanol?

The Gauche effect in 2-fluoroethanol is caused by steric hindrance between the fluorine and hydroxyl groups. The fluorine atom is larger than the hydrogen atom in ethane, which causes it to prefer a gauche position to minimize repulsive interactions.

How does the Gauche effect affect the physical properties of 2-fluoroethanol?

The Gauche effect can affect the physical properties of 2-fluoroethanol, such as melting and boiling points, by influencing the overall shape and structure of the molecule. In general, a more compact and symmetrical molecule will have higher melting and boiling points due to stronger intermolecular forces.

Is the Gauche effect specific to 2-fluoroethanol?

No, the Gauche effect is a common phenomenon in molecules with bulky substituents. It is particularly pronounced in 2-fluoroethanol due to the size difference between fluorine and hydrogen, but can also be observed in other molecules with similar groups.

How is the Gauche effect important in organic chemistry?

The Gauche effect is important in organic chemistry because it can affect the reactivity and selectivity of reactions. In some cases, the preference for a gauche conformation can hinder or facilitate certain reactions, making it a useful concept in understanding and predicting chemical behavior.

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