page 10 Flashcards
Weakly Polar Molecules:
Alkyl halides are weakly polar molecules due to the polar nature of the carbon-halogen (C-X) bond.
The halogen (X) is more electronegative than carbon, creating a dipole moment with a partial negative charge (δ−) on the halogen and a partial positive charge (δ+) on the carbon.
Dipole-Dipole Interactions:
These polar C-X bonds lead to dipole-dipole interactions between neighboring molecules.
Example: In chloromethane (
CH3Cl), the Cl atom has δ−, and the C atom bonded to it has
δ +, allowing neighboring molecules to align their opposite charges.
No Hydrogen Bonding:
Alkyl halides lack hydrogen atoms bonded to highly electronegative atoms (O, N, F).
As a result, they cannot form hydrogen bonds, unlike molecules like water or alcohols.
Implications for Properties:
The weak polarity and absence of hydrogen bonding affect:
Boiling Points: Higher than nonpolar alkanes but lower than alcohols.
Solubility: Insoluble in water (no hydrogen bonding) but soluble in organic solvents.
Why are alkyl halides polar molecules?
Answer: Because of the polar carbon-halogen (C-X) bond, where the halogen is more electronegative than carbon.
What type of interactions do alkyl halides exhibit between molecules?
Answer: Dipole-dipole interactions.
Why can’t alkyl halides form hydrogen bonds?
Answer: They lack hydrogen atoms bonded to highly electronegative atoms (O, N, or F).
Are alkyl halides soluble in water? Why or why not?
Answer: No, they are insoluble in water because they cannot form hydrogen bonds.
In CH3Cl, which atom has a partial negative charge (δ− )?
Answer: Chlorine (Cl).
What type of interaction occurs between the dipoles of neighboring alkyl halide molecules?
Answer: The positive end (δ+ ) of one molecule interacts with the negative end (δ −) of another.
