DAT: OC Question of the Day ( 6/21 )

[AshDDS2B]

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Arrange the following alkanes in order of decreasing boiling points without referring to tables:

A. n-hexane
B. 3-methylpentane
C. 2,2-dimethylbutane
D. n-heptane
E. 2-methylpentane

( Try to explain your answer )

I'll post the answer tonight.

 

[DrTacoElf]

Boiling point is based on two things for these molecules. Ammount of branching (as this incresase BP decreases because vanderwaals forces between molecules decrease due to decreasing surface area) and chain length (MW) as this increases so does BP.

In Decreasing Order of BP

n-heptane, n-hexane, 3-methylpentane, 2-methylpentane, 2,2 dimethyl butane

I can not reason between 3 and 2 methylpentane, but i'm gonna guess 2-methylpentane has a lower BP b/c its more terminal.

 

[DrTacoElf]

BP of 3-methylpentane: 63.3?C
BP of 2-methylpentane: 60.0?C

👍

 

[AshDDS2B]

d>a>b>e>c