Show A Possible Hydrogen Bond Between Methanol (CH3OH) And Dimethyl Ether (CH3OCH3) Label The Donor And The Acceptor. Is There More Than One Possible Hydrogen Bond Between More Than One Possible Heni OCH) These Two Molecules? Explain
The Correct Answer and Explanation is :
To illustrate the possible hydrogen bond between methanol (CH₃OH) and dimethyl ether (CH₃OCH₃), let’s first define the hydrogen bond donor and acceptor:
- Hydrogen Bond Donor: The molecule providing the hydrogen atom attached to a highly electronegative atom (like O, N, or F). In this case, methanol acts as the donor because the hydroxyl (-OH) group has a hydrogen bonded to oxygen.
- Hydrogen Bond Acceptor: The molecule providing the electronegative atom with lone pairs to interact with the donor hydrogen. Dimethyl ether acts as the acceptor due to the oxygen atom in the ether group having lone pairs of electrons.
Possible Hydrogen Bond:
The hydrogen bond forms between the hydrogen atom of methanol’s hydroxyl group (-OH) and one of the lone pairs on the oxygen atom in dimethyl ether. This bond is depicted as:
[ CH₃OH \cdots O(CH₃)₂ ]
Here:
- Methanol is the donor (H attached to O).
- Dimethyl ether is the acceptor (O atom with lone pairs).
Multiple Hydrogen Bonds:
There is only one possible hydrogen bond between methanol and dimethyl ether. Methanol has only one hydrogen in its -OH group to donate. Dimethyl ether has one oxygen atom capable of accepting hydrogen bonds. Therefore, only a single hydrogen bond forms between these molecules.
Explanation (300 Words):
Hydrogen bonding is a type of intermolecular force that occurs when a hydrogen atom covalently bonded to an electronegative atom interacts with a lone pair on another electronegative atom. In this case, methanol contains a polar hydroxyl group (-OH), where the hydrogen is partially positive and the oxygen is partially negative due to electronegativity differences. Dimethyl ether contains an oxygen atom with lone pairs of electrons, making it an ideal hydrogen bond acceptor.
When methanol and dimethyl ether are in proximity, the partially positive hydrogen atom of methanol’s -OH group is attracted to the lone pair on the oxygen of dimethyl ether. This interaction forms a hydrogen bond, denoted by a dotted line between the hydrogen and the oxygen atoms. The strength of this bond is moderate, weaker than covalent bonds but stronger than van der Waals forces.
It’s important to note that although both methanol and dimethyl ether contain oxygen atoms, only methanol can act as a donor because it has an -OH group with a directly bonded hydrogen atom. Dimethyl ether lacks such a group and can only accept hydrogen bonds. Hence, only one hydrogen bond can form between these molecules. This interaction plays a significant role in determining the physical properties of mixtures containing these compounds, such as boiling points and solubility.