Sophomore organic chemistry questions about homologs and isomers

Written on the front: ch3=chch2ch3 in the question stem - typo right? It should be ch2=chch2ch3.

First of all, understand the concept: 1. Homologues: substances that differ by one or several CH2 atomic clusters in molecular composition are called homologues to each other.

2. Isomers: Compounds with isomerism (compounds with the same molecular formula but different structures) are called isomers with each other. 3. Addition reaction:

A reaction in which the unsaturated carbon atoms in an organic molecule are directly combined with other atoms or clusters of atoms to form new compounds.

Answer: The congeners are different from the CH2 clusters, so exclude , and then look at the number of carbon and hydrogen in the remaining structure short. So (1) belongs to the homologue: 1 and 8

As the name suggests, isomers look at the same molecular formula, so (2) those that belong to isomers are: 2 and 3 and 4; 5 vs. 6

The addition reaction occurs in substances with double or triple bonds, so (3) the addition reaction can occur under certain conditions

I'll teach you how.

1. The concept of homologues: a series of compounds in organic compounds that have the same general formula, differ in composition by one or more atomic clusters, and are similar in structure and properties.

2. The concept of isomers: substances with the same molecular formula and different structures (functional group position isomerism, category isomerism, carbon chain isomerism).

3. Substances that react with addition generally have unsaturated bonds (such as carbon-carbon double and triple bonds).

Homologue: A substance with the same number of functional groups and the same molecular formula difference of one or several CH2.

Isomers: The molecular formula is the same and the structure is different.

Knowing these two concepts can be judged.

1 1 and 82 234 5 and 6

3 12348 Select if there is an unsaturated key.

C3H8 is a saturated hydrocarbon, and the C value is less than 4, so there is only one.

C4H8 is an unsaturated hydrocarbon, respectively

CH3-CH = CH-CH3 (2-butene) CH2 = CH-CH2-CH3 (1-butene).

ch2-ch2丨. 丨.

CH2-CH2 (cyclobutane).

There is no shortcut to finding isomers, and generally speaking, it is best to list them all, without duplication or omission.

First of all, this high school isomerism only talks about the isomerism in the plane, such as C-chain isomerism, functional group isomerism, and functional group position isomerism. If it is a high school chemistry competition or organic chemistry in college, it will also talk about stereoisomerism, such as optical isomerism.

1.In high school, what you call C5H10 is to consider the case of a straight chain with a double bond.

2.In high school, according to the chemical formula, the structural judgment made is a possible structure, so in addition to telling you that it is benzene ring, fused ring, and naphthalene, the chain structure should be considered.

3.Even if you talk about alkanes, they don't have to be chains, only saturated alkanes are necessarily chained.

ch3ch2ch2ch2ch2ch2ch2ch3, heptane.

ch3ch2ch2ch2ch(ch3)2

2-Methylhexane.

CH3CH2CH2CH(CH3)CH2CH33-methylhexane.

CH3CH(CH3)CH(CH3)CH2CH32,3-Dimethylpentane.

CH3CH(CH3)CH2CH(CH3)CH32,4-dimethylpentane.

ch3c(ch3)2ch2ch2ch3

2,2-Dimethylpentane.

ch3ch2c(ch3)2ch2ch3

3,3-Dimethylpentane.

CH3CH2CH(CH2CH3)CH2CH32-ethylpentane.

ch3c(ch3)ch(ch3)2

2,2,3-Trimethylbutane.

c-c-c-c-c-c-c

c-c-c-c-c-c

cc-c-c-c-c-c

~cc-c-c-c-c

~c-c~c

c-c-c-c-c,~!

c~~~cc-c-c-c-c

c~~~cc-c-c-c-c

~c~cc-c-c-c-c

~c~c~~c

c-c-c-c~c

ch3ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2ch2

ch3ch2ch2ch2ch(ch3)2

2-Methylhexane.

CH3CH2CH2CH(CH3)CH2CH33-methylhexane.

CH3CH(CH3)CH(CH3)CH2CH32,3-Dimethylpentane.

CH3CH(CH3)CH2CH(CH3)CH32,4-dimethylpentane.

ch3c(ch3)2ch2ch2ch3

2,2-Dimethylpentane.

ch3ch2c(ch3)2ch2ch3

3,3-Dimethylpentane.

CH3CH2CH(CH2CH3)CH2CH32-ethylpentane.

ch3c(ch3)ch(ch3)2

2,2,3-Trimethylbutane.

Through symmetry, it can be seen that the carbon atomic sequence number of equivalent hydrogen is , and the product structure after equivalent hydrogen substitution is the same, so there are only 5 isomers.

The phenanthrene is numbered 1 10 where there is an axis of symmetry, so 1,8 2,7 3,6 4,5 9,10 These five pairs are equal in position.

Therefore, there are 5 kinds of monochlorine substitutes for phenanthrene.

Question: Since there is symmetry of the ring in the middle, why are there 5 and why is it not 1?

It's just that there is an axis of symmetry, not about the ring symmetry in the middle.

From the perspective of the spatial structure of the phenanthrene, the phenanthrene is not on the same plane, so it is not symmetrical about the ring in the middle, you can draw its structure to understand.

Not exactly, both of these are mostly definitions of organic compounds, so most of the objects oriented are organic compounds.

Homologues generally refer to organic compounds, but isomerism is not necessarily, such as silver thunderate and silver cyanate, both of which are inorganic but also isomers.

Below are the definitions of both.

Homologues: Chemically, we refer to compounds with similar structures and molecular composition differing by one or more CH2 clusters as homologues. It is mostly used for organic compounds.

Isomers are also known as isomers. In chemistry, it refers to molecules that have the same molecular formula; The chemical bonds between atoms are also often the same; But the arrangement of the atoms is different. In other words, they have different "structural formulas".

Many isomers have the same or similar chemical properties. The phenomenon of isomerism is one of the reasons for the large variety and quantity of organic compounds.

The basis of isomers is the isomer of alkanes, and it is necessary to be proficient in writing basic substances, and then expand to the derivatives of hydrocarbons, from carbon chain isomerism, position isomerism and functional group isomerism to write, all three cases together are that there are several structural formulas of an organic matter.

Regarding whether the substitution of different structures will be affected or not, the substitution depends on the equivalent hydrogen atoms of different isomers are different, and the substitution products are also different. For example, n-butane C-C-C-C, there are two hydrogen atoms, there are two kinds of monochlorine substitutes, and there are two hydrogen atoms in isobutane C-C(CH3)-C, and there are two hydrogen atoms (H on the three methyl groups and H on the middle 2C), and there are also two kinds of monochlorinated substances, so there are 4 kinds of monochlorinated substances in C4H10, and the structure of these four substances is different, so the properties are also different.

The addition is simpler, for example, c=c-c-c and c-c=c-c are isomers, which are different from bromine water addition products.

Don't worry, organic chemistry is very regular, not scattered like inorganic chemistry. Instead of "how many structural formulas does an organism have", give you a molecular formula, ask you how many isomers it has (these isomers are called isomers of this molecular formula), and ask you about the corresponding properties of these isomers, which usually have the following types:1

This is mainly the position of the double or triple bond, and the different positions will also affect the structure; 3.Species isomerism: For example, ketones and aldehydes are isomers, and acids and esters are isomers.

That's probably all there is to it.

A C2 axis of symmetry has a total of 5 substitutions, so there are 5 kinds of monochloride substitutes in phenanthrene.

Be careful not to confuse with benzene, which has 6 C2 axes of symmetry!

1 Chlorine, dear. You can just scratch it and see that it is precisely because the parent body is about the axis symmetry in the middle, so there are only 5 kinds, or more. Because there is a symmetry axis in the middle of the parent body, there are 5 different positions after symmetry, so there are 5 kinds of 1 chlorinated substances.

There is only one axis of symmetry, and one side of the axis of symmetry can be replaced by five positions, so there are five types.

Draw a symmetry axis in the middle and then symmetry left and right, in which there are a total of 10 places where phenanthrene monochloride substitutes can be produced, but 5 pairs are the same, so there are only 5 kinds.

This one is axisymmetric, not central.