Boiling Points of Organic Compounds

Boiling Points of Organic Compounds 1
BOILING POINTS OF ORGANIC COMPOUNDS
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Boiling Points of Organic Compounds 2
Boiling Points of 3-Methylbutanal, Butanoic Acid, Hexanal, And Pentanal
Introduction
Boiling point is a temperature at which the fluid’s (normally liquid) vapour pressure matches the
outside pressure surrounding it. Variation in chemicals boiling points is due to difference in their
chemical compositions (Timberlake, k. 2015). Determination of the boiling points can only be
attained experimentally, by taking the measurements. The compounds named above are all
organic compound.
Table 1. Compounds and their boiling points at a pressure of 760 mmHg
Compound Boiling points in degrees Celsius at
760 mmHg
Molecular weight (g/ mol)
Butanoic Acid 164.3 ± 3.0 88.11
Hexanal 127.9 ± 3.0 100.17
Pentanal 103.7 ± 3.0 86.13
3-Methylbutanal 92.5° 86.13
Order of the boiling points
Butanoic Acid
Hexanal
Pentanal
3-Methylbutanal.
Factors Affecting the Boiling Points of the Organic Compounds
Reducing
boiling points

Boiling Points of Organic Compounds 3
The boiling points reveal the strength of forces among the molecules. The more they bond
together, the more energy it will take to discharge them into the air as gases. The following
factors determine the boiling points of the compounds subjected to the same external factors like
the atmospheric pressure (Sherwood & Dalby, 2018).
Nature of the intermolecular forces.
The intermolecular forces between the molecules of the organic compounds are: ionic, hydrogen
bonding, dipole to dipole forces and the Van der Waals dispersion forces. Their strength reduces
in that order, ionic bonding being the strongest and the Van der Waals dispersion forces being
the weakest.
Polarity
This is the attraction between the molecules of a liquid as a result of a significant differences in
electronegativity between two or more elements making up the liquid molecules (Carey et al.,
2018). Some of the organic molecules are dipolar.
In polar compounds the elements with the unlike polarities attract each other, meaning the
positive end is attracted to the negative end of another molecule. The resultant charge effect
causes the molecules to attract each other. Functional group determines the polarity of a given
molecule. The more the functional groups the greater the polarity. And the greater the polarity
the higher the boiling points (Anon 2019).
The molecular weight