Why are smaller alcohols fully miscible with water while larger alcohols have lower solubility in water?
A. In larger alcohols, the polar hydrocarbon chain cannot interact with polar water molecules and limits alcohol's ability to interact with water.
B. In larger alcohols, the non-polar hydrocarbon chain cannot interact with polar water molecules and limits alcohol's ability to interact with water.
C. In larger alcohols, the non-polar hydrocarbon chain cannot interact with non-polar water molecules and limits alcohol's ability to interact with water.
D. In larger alcohols, the polar hydrocarbon chain cannot interact with non-polar water molecules and limits alcohol's ability to interact with water.
A and D can't be right because of the "molar hydrocarbon chain" statement.
Between B and C you make the choice on whether H2O is a polar or a non-polar molecule.
H2O is polar so B right?
That's what I would choose.
The correct answer is B. In larger alcohols, the non-polar hydrocarbon chain cannot interact with polar water molecules and limits alcohol's ability to interact with water.
To understand why smaller alcohols are fully miscible with water while larger alcohols have lower solubility in water, we need to look at the molecular structure of alcohols and their interactions with water.
Alcohols consist of a hydrocarbon chain with a hydroxyl (-OH) group attached. The hydroxyl group is polar because oxygen is more electronegative than hydrogen, giving it a partial negative charge (δ-) and the hydrogen a partial positive charge (δ+). The polar nature of the hydroxyl group allows alcohols to form hydrogen bonds with water molecules.
Water is a polar molecule, with oxygen having a partial negative charge (δ-) and hydrogen having a partial positive charge (δ+). This polarity allows water molecules to form hydrogen bonds with each other and with other polar molecules like alcohols.
When smaller alcohols, such as methanol (CH3OH) or ethanol (C2H5OH), dissolve in water, the polar hydroxyl group of the alcohol forms hydrogen bonds with water molecules. Additionally, the smaller hydrocarbon chains of these alcohols can interact with water through van der Waals forces. As a result, smaller alcohols are fully miscible with water because both the polar hydroxyl group and the hydrocarbon chain can interact effectively with water.
On the other hand, larger alcohols, such as octanol (C8H17OH) or decanol (C10H21OH), have longer hydrocarbon chains. These hydrocarbon chains consist of non-polar carbon and hydrogen atoms that do not readily interact with the polar water molecules. The non-polar hydrocarbon chain tends to cluster together, minimizing its contact with water. As a result, the solubility of larger alcohols in water decreases because the non-polar hydrocarbon chain limits the ability of the alcohol molecule to interact with the polar water molecules through hydrogen bonding.