Introduction:
Ethylene glycol is a molecule with two hydroxyl groups (-OH) attached to a carbon chain. It can exist in three different conformations: eclipse, anti, and gauche. The stability of these conformations is determined by the interaction between the hydroxyl groups and the steric hindrance caused by the carbon chain. In this response, we will discuss the increasing order of stability among these conformations and explain the reasons behind it.

Increasing Order of Stability:
The increasing order of stability among the three main conformations of ethylene glycol is as follows:

1. Eclipse Conformation
2. Gauche Conformation
3. Anti Conformation

Explanation:

Eclipse Conformation:
In the eclipse conformation, the hydroxyl groups are positioned directly in front of each other, resulting in maximum steric hindrance. This conformation is the least stable due to the repulsion between the electron-rich oxygen atoms of the hydroxyl groups. The steric hindrance causes strain in the molecule, leading to higher energy and instability.

Gauche Conformation:
In the gauche conformation, the hydroxyl groups are positioned next to each other, but not directly in front. This conformation is more stable than the eclipse conformation because the steric hindrance is reduced. The hydrogen atoms of the hydroxyl groups are placed further apart, minimizing the repulsion between the oxygen atoms. However, there is still some steric hindrance, which contributes to the overall instability of this conformation.

Anti Conformation:
In the anti conformation, the hydroxyl groups are positioned opposite to each other. This conformation is the most stable among the three because there is minimal steric hindrance. The hydrogen atoms of the hydroxyl groups are far apart, allowing for a favorable arrangement without repulsive interactions. The anti conformation is energetically favored and represents the lowest energy state of ethylene glycol.

Conclusion:
In conclusion, the increasing order of stability among the three main conformations of ethylene glycol is eclipse, gauche, and anti. The eclipse conformation is the least stable due to maximum steric hindrance, while the anti conformation is the most stable with minimal steric hindrance. The stability of these conformations is determined by the repulsion between the oxygen atoms of the hydroxyl groups and the arrangement of hydrogen atoms.