Propanol is higher largely because it is a larger molecule (molar mass is higher) and higher dispersion forces.
Are you sure the ionic character is higher in LiI? Li has electronegativity (EN) of about 0.98, K is about 0.82.
Consider the molecules ether (CH3OCH3), ethyl alcohol (CH3CH2OH), and propanol (CH3CH2CH2OH) (not isopropanol!).
The boiling point of ether is -25 degrees while the boiling point of ethyl alcohol is 78 degrees. How would you explain the difference in properties of the two molecules that explains why the difference in boiling points is so large?
Answer: Ethyl alcohol undergoes, hidrogen bonding while eter does not
Now compare the boiling point of ethyl alcohol (78 degrees) with that of propanol (98 degrees). How would you explain the difference in properties of the two molecules that explains the difference in boiling points?
Answer: Propanol is larger than ethyl alcohol, and therefore more polarizable.
Which molecule ( LiI or KI ) has the lower boiling point?
Answer: LiI because this is more ionic character than KI.
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