Which of these substances is the most soluble in water? a. CH3(CH2)2 CH2 NH2 b. CH3(CH2)4 CH2 Cl

Which of these substances is the most soluble in water? a....

Which of these substances is the most soluble in water? a. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}$ b. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CH}_{2} \mathrm{Cl}$ c. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{CH}_{2} \mathrm{Br}$ d. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{8} \mathrm{CH}_{2} \mathrm{I}$

Which of these substances is the most soluble in water?
a. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}$
b. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{4} \mathrm{CH}_{2} \mathrm{Cl}$
c. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{CH}_{2} \mathrm{Br}$
d. $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{8} \mathrm{CH}_{2} \mathrm{I}$

Key Concepts

Hydrogen Bonding

Hydrogen bonding is a type of strong dipole-dipole interaction that occurs when hydrogen is covalently bonded to a highly electronegative atom such as oxygen, nitrogen, or fluorine. Molecules capable of hydrogen bonding typically exhibit enhanced solubility in water because they can form multiple hydrogen bonds with water molecules, facilitating dissolution.

Alkyl Chain Length Effects

The alkyl chain length of a molecule affects its solubility due to the balance between hydrophilic and hydrophobic properties. As the length of the non-polar alkyl chain increases, the hydrophobic character of the molecule is enhanced, which can reduce water solubility. This factor is particularly important when comparing molecules that have similar polar functional groups but differing alkyl chain lengths.

Water Solubility

Water solubility refers to the ability of a substance to dissolve in water. This property is influenced by the molecule's polarity and its ability to interact with water molecules. Substances that closely match water’s polarity typically have higher solubility in water due to favorable intermolecular interactions, such as hydrogen bonding or dipole-dipole forces.

Polarity

Polarity is a measure of the distribution of electrical charge across a molecule. Polar molecules have regions of partial positive and negative charges, which enables them to interact with polar solvents like water. The presence of electronegative atoms and polar bonds enhances the polarity, thereby increasing solubility in water.

Transcript

00:02 Hello, in this question we want to know which of the molecules given to us there would be most soluble in water.

00:10 So to answer that question we need to remember a phrase concerning solubility.

00:15 It says like dissolves like.

00:22 So the more similar a solute and its solvent are, the more likely the solute is to dissolve in that solvent.

00:30 And what we're typically referring to here in terms of similarity is polarities.

00:38 Because nonpolar solutes dissolve in nonpolar solvents.

00:57 Whereas polar solutes as well as ionic solutes have charges.

01:08 So they dissolve best in polar solvents.

01:30 So what you should be noticing here is that it comes down to intermolecular forces.

01:37 The more similar their intermolecular forces, the more likely they are to dissolve.

01:42 So similar intermolecular forces between the molecules are more likely to dissolve than each other.

02:03 Which brings us to this question then.

02:07 We have our solvent is water and water is a bent molecule.

02:21 So it is polar and since it has o to h bonds, it participates in hydrogen bonding as its strongest intermolecular force.

02:33 And if we recall hydrogen bonding occurs between molecules that are polar with nitrogen to hydrogen, fluorine to hydrogen, or oxygen to hydrogen bonds...

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