"Understanding Organic Compounds" Simple Organic Compounds PPT (Lesson 2)

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"Understanding Organic Compounds" Simple Organic Compounds PPT (Lesson 2)

Part 1: Essential knowledge and foundation of literacy

1. Common functional groups in organic compounds

1. Experimental research

2. Related concepts

(1) Derivatives of hydrocarbons: organic compounds in which the hydrogen atoms in the hydrocarbon molecules are replaced by _______________.

(2) Functional group: An atom or atomic group in an organic compound molecule that is relatively lively, easy to react, and reflects the _________ of a certain type of organic compound.

(3) Classify organic matter according to functional groups (fill in the name of the functional group of the relevant organic matter)

【Situation·Thinking】

More than 300 years ago, the famous chemist Boyle discovered the color reaction between iron salts and gallic acid, and thus invented blue-black ink. The simplified structural formula of gallic acid is shown in the figure. What functional groups does gallic acid contain?

Hint: hydroxyl and carboxyl groups.

[Think about it] For any kind of organic matter, it can belong to different categories according to different classification standards. Please think about which categories CH3COOCH3 can belong to?

Tip: In terms of the elements it contains, it is a derivative of hydrocarbons; in terms of the functional groups it contains, it is an ester.

2. Isomerism and isomers

1. Isomerism: The phenomenon that compounds have the same _______ but different _________ is called isomerism.

2. Isomers: Compounds that are _______ the same but _______ different are isomers of each other.

3. Rule: The more carbon atoms there are in an organic substance, the more isomers there are. For example, butane has two isomers, and pentane has three isomers.

(1) According to the structural formulas of n-butane and isobutane, fill in the spaces in the following table:

【Smart Judgment】

(1) Organic substances with the same relative molecular mass but different structures are isomers of each other. ()

Tip:×. Compounds with the same molecular formula but different structures are isomers of each other.

(2) Substances represented by the chemical formula C4H10 are not necessarily pure substances. ()

Tips:√. A substance with the molecular formula C4H10 may be n-butane or isobutane.

(3) Isomers have the same physical properties but different chemical properties. ()

Tip:×. Isomers are different substances and therefore have different physical and chemical properties.

【Situation·Thinking】

Cyanic acid is a volatile and corrosive liquid with a strong bitter almond odor. German chemist Weller determined the chemical composition of cyanic acid (HCNO). At the same time, another German chemist Liebig determined the chemical composition of a kind of "fulminant acid" (HOCN), which was actually the same as cyanic acid! How can different compounds have the same composition?

Understanding Organic Compounds PPT, Part 2: Key Competencies·Quality Foundation

Knowledge Points: Writing and Judgment of Isomers

[Key points to clarify doubts]

1. Writing of Alkane Isomers

Alkanes only have carbon chain isomerism. When writing alkane isomers, the "carbon reduction method" is generally used, which can be summarized as "two notes, three principles, and four sequences."

Such as the isomers of C6H14:

(1) Connect all the carbon atoms in the molecule into a straight chain as the main chain.

C—C—C—C—C—C

(2) Take a carbon atom from one end of the main chain as a branch chain (i.e. methyl group), and connect it to each carbon atom on one side of the central symmetry line (dashed line) of the main chain. At this time, there are two types of carbon skeletons:

Note: The methyl group cannot be connected to the ① and ⑤ positions, otherwise it will be the same as the straight chain situation. The ② and ④ positions are equivalent, and only one can be used, otherwise it will be repeated.

(3) Remove two carbon atoms from the main chain as a branch chain (i.e. ethyl) or two branch chains (i.e. 2 methyl groups) and connect them to each carbon on one side or both sides of the central symmetry line of the main chain. Atomically, there are two types of carbon skeleton structures at this time:

Note: No ethyl group can be connected to the ② position or ③ position, otherwise there will be 5 carbon atoms in the main chain. So there are 5 isomers of C6H14.

2. Judgment of the number of isomers of monovalent substitution products of hydrocarbons

(1) The "equivalent hydrogen" method can be used to judge the monovalent substitution products of hydrocarbons. The so-called "equivalent hydrogen" refers to hydrogen atoms with equivalent positions. There are several equivalent hydrogen atoms in hydrocarbons, and there are several types of monovalent substitution products.

(2) Method of judging equivalent hydrogen atoms.

①Hydrogen atoms connected to the same carbon atom are equivalent.

If the four hydrogen atoms in the CH4 molecule are equivalent, there is only one monochloride of methane.

[Error-prone reminder] 4 "certain" and "not necessarily" about isomers

(1) Isomers must have the same constituent elements, but those with the same constituent elements are not necessarily isomers.

(2) Isomers must have the same relative molecular mass, but those with the same relative molecular mass are not necessarily isomers.

(3) The mass fraction of each element in isomers must be the same, but elements with the same mass fraction are not necessarily isomers.

(4) The simplest formulas of isomers must be the same, but compounds with the same simplest formula are not necessarily isomers.

【Think·Discussion】

(1) Are the simplest formulas, relative molecular masses, percentages of each element, and melting and boiling points necessarily the same between isomers?

Tip: The molecular formulas of isomers are the same, so their simplest formula, relative molecular mass, and percentage content of each element must be the same, but the melting and boiling points are different.

(2) Do all alkanes have isomers? Give an example.

Tip: Not all alkanes have isomers. Methane, ethane and propane do not have isomers.

【Compensation training】

1. Which of the following molecular formulas represents only one substance ()

A.C4H10B.C5H12C.CHCl3D.C2H4Cl2

[Analysis] Choose C. Item A, C4H10 can represent n-butane or isobutane; Item B can represent n-pentane, isopentane or neopentane; Item C, CHCl3 only represents chloroform; Item D, C2H4Cl2 can represent CH2ClCH2Cl or CH3CHCl2; Item C correct.

2. (2019·Hefei Senior High School Test) Among the organic compounds with the following structures:

①CH3CH2CH2CH2CH3

②CH3CH2CH2CH2CH2CH3

The correct combination of isomers is ()

A.②and⑤B.②and③

C. ① and ② D. ③ and ④

[Analysis] Choose B. ① and ④, ② and ③ have the same molecular formula but different structures, and are isomers respectively; ② and ⑤ are the same substance.

Knowledge correlation and literacy application

【Literacy transfer】

1. In the current home appliance market, fluorine-free refrigerators are called green refrigerators. Its major improvement is that it does not use Freon-12 but uses a new refrigerant (R-134a) as the refrigerant. The correct statement about Freon-12 (CCl2F2) is ()

A. There are two isomers

B. It is a planar molecule

C. There is only one structure

D. There are four isomers

[Analysis] Choose C. CCl2F2 can be regarded as the replacement of two hydrogen atoms of CH2Cl2 by two fluorine atoms, so C is chosen.

2. (2019·Nanping High School Grade 1 Test) Which of the following relationships among the following substances is incorrect ()

A.CH3CH2CH2CH2CH3 and are isomers of each other

B. Dry ice and ice are the same substance

C.CH3CH3 and CH3CH2CH3 are homologues of each other

D.12C and 14C are isotopes of each other

[Analysis] Choose B. Dry ice is carbon dioxide crystals, and ice is solid water.

3. (2019·Baoding High School Detection) Propane (C3H8) is commonly used as a fuel for barbecues, portable stoves and motor vehicles. It is often used to drive buses and taxis, and is also used as fuel for heating and cooking in RVs and camping. Sports torches also generally use propane as fuel.

(1) What are the advantages of using propane as fuel?

(2) How many monochlorine substitution products are there for propane?

Answer: (1) The products of complete combustion of propane are carbon dioxide and water, which will not produce pollution.

(2) There are two monochlorine substitution products of propane, namely CH3CH2CH2Cl and CH3CHClCH3.

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Update Time: 2024-07-03

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