High school chemistry,Often involves the concept of isomers of organic matter,More difficult to master.Here,Tell everyone the only technique for judging isomers.
1. Reasons for the variety of organic matter
There are many types and quantities of organic compounds.the reason is:
1.1 magical carbon atom
A C atom can form four chemical bonds,Both can be atoms of other elements,C atoms can also be combined with each other,Form a relatively stable chemical bond.
1.2 magical carbon skeleton
Carbon atoms in organic matter,There are a variety of three-dimensional spatial arrangements,Most of them exist in the form of regular tetrahedrons,It can also exist in a flat triangular or linear structure.
There are currently more than 30 million compounds in the world,The number of organic matter exceeds 20 million.
(3) Five types of bonds between carbon atoms
Carbon atoms can form four covalent bonds,You can do it yourself: ①single bond, ②double bond, ③triple bond, ④chain, ⑤ring, etc. (Single bond, double bond and ring are the main ones in middle school),All easily confused vision.
2. How to judge the structure and quantity of isomers
Judge the isomers of organic matter,the most important is:
According to the chemical formula,Judge how many double bonds, triple bonds, and rings there are?
Introduce a concept of unsaturation,
1) C=C double bond
The degree of unsaturation of a C=C double bond is 1;
The degree of unsaturation of a ring is 1;
3) Carbon-carbon triple bond
The degree of unsaturation of the carbon-carbon triple bond is 2.
The concept of unsaturation,You will learn it in college.
We already know some general structural formulas of hydrocarbons:
2.2 General formula of organic matter
1) Alkanes: general formula CnH2n+2.(Satisfying this general formula,The degree of unsaturation is 0.)
Contains only C-C single bond,Does not contain double bonds, triple bonds and rings;
2) Olefins: general formula CnH2n.(Compared with alkanes,For every 2 H atoms missing,Is an unsaturation)
The degree of unsaturation of this general formula is 1,and so,May contain a C=C double bond,Or contain a ring,Does not contain three keys;
3) Alkynes: general formula CnH2n-2.
The degree of unsaturation of this general formula is 2.
May contain a carbon-carbon triple bond,Or other situations (double bond, ring unsaturation are all 1,Combination of the two,Three situations);
The above knowledge,Everyone knows it.
4) Heteroatom problem
In practical applications,Heteroatoms other than C and H often appear,How to judge the degree of unsaturation?
The trick is here:
For every additional heteroatom,Then in terms of the number of H atoms,"Plus 2,Subtract the valence of this heteroatom."
It's that simple!
3. Examples of judging isomers
Example 1: If the chemical formula of an organic substance contains halogens (F, Cl, Br, I),它们的化合价都是1，每含有一个卤素原子，则加上2，再减去它们的化合价1（＋2－1＝1），结果还是1。