1. There are numerous organic compounds that form their own systems
There are two main reasons for the large number of organic compounds: (1) carbon atoms can combine with each other in various ways to form stable, linear, branched, or cyclic compounds of different lengths; (2) Carbon is an element in the second period and fourth group of the periodic table. It can not only bind with hydrogen atoms with low electronegativity, but also form chemical bonds with elements such as oxygen, sulfur, and halogens with high electronegativity.
Although there are many organic compounds, they can be unified into a complete system based on their interrelationships.

2. Poor thermal stability and easy combustion
Compared to typical inorganic compounds, organic compounds are generally unstable to heat, and some can even decompose at room temperature. Although most organic compounds are stable at room temperature, when heated in a crucible, they undergo carbonization and turn black, leaving no ash after complete combustion (except for salts of organic acids). This is one of the simple methods for identifying organic compounds.

3. Low melting point
The melting point of organic compounds is usually lower than that of inorganic compounds, usually melting below 300 ℃.

4. Difficult to dissolve in water, easily soluble in organic solvents
Most organic compounds are easily soluble in organic solvents but difficult to dissolve in water. However, when organic compound molecules contain hydroxyl groups, sulfonic groups, etc. that can form hydrogen bonds with water, the organic compound may also be soluble in water.

5. Slow reaction speed and frequent occurrence of side reactions
Although there are some substances with high ionization degree in organic acids and organic bases, most organic compounds have low ionization degree. So, many organic reactions are generally slow molecular reactions that require heating or the use of catalysts, and instantaneous ion reactions are rare. In addition, decomposition or substitution reactions occur at a certain part of the molecule, and in most cases, the reaction proceeds in stages. So, often by-products are generated or multiple reaction intermediates can be separated.