Melting Boiling Temperature Hydrocarbons Alkane Alkene Benzene Aromatic Alcohol Acid Naphthalene

Overview

Engineering reference data for Melting Boiling Temperature Hydrocarbons Alkane Alkene Benzene Aromatic Alcohol Acid Naphthalene in thermodynamics.

Key Formulas

First Law

$\Delta U = Q - W$

Energy is conserved — heat added minus work done.

Ideal Gas Law

$PV = nRT$

Relates pressure, volume, and temperature of an ideal gas.

Heat Transfer

$Q = mc\Delta T$

Sensible heat transfer.

Carnot Efficiency

$\eta = 1 - T_C/T_H$

Maximum efficiency between two temperatures.

Variables

Hydrocarbon Classification and General Formulas

General molecular formulas for the main hydrocarbon families:

Where $n$ = number of carbon atoms.

Boiling Point Trend

For hydrocarbons with the same carbon number, boiling points increase in the following order:

1. Multi-substituted alkanes (e.g., 2,2-dimethylalkane) — lowest
2. Single-substituted alkanes (e.g., 2-methylalkane)
3. Single-substituted alkenes (e.g., 2-methylalkene)
4. Normal alkenes (1-alkene)
5. Normal alkanes (n-alkane)
6. Alkylcyclohexanes
7. Alkylbenzenes
8. Cycloalkenes / Cycloalkanes
9. 2-Alkanols / 4-Alkanols / 1-Alkylnaphthalenes
10. 1-Alkanols
11. Normal alkanoic acids — highest

Key principle: Branching lowers boiling point (reduced surface area for intermolecular forces), while hydrogen bonding functional groups (alcohols, carboxylic acids) and ring structures significantly raise it.

Boiling Points of Hydrocarbons, Alcohols and Acids (°C)

References

• Original Source