What are the rules of the structure of chemical organics i.e., isomers ?

Are you talking about the different structural formulas of an organic matter, if that is an isomer, a thing that must be tested for general organic inference, the result of the structure will be the reaction that can occur in each group to infer what the group is, and the reaction that can occur in different positions of the group in the structural formula is also different, look at how many hydrogen there are on the carbon directly connected to him, I think you still don't know enough about the knowledge or don't remember well, there are many organic knowledge points, and miscellaneous, you can get a table out, just take a look at it!

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.

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.

The essence of isomers produced by organic matter lies in the different order of atoms, which mainly refers to the following three situations in secondary school:

Carbon chain isomerism: isomerism caused by different attachment orders of carbon atoms, such as ch3ch(ch3)ch3 and ch3ch2ch2ch3

Functional group position isomerism: Isomerism caused by the different positions of functional groups, such as: ch3ch2ch=ch2 and ch3ch=chch3

Heterogeneous isomerism of functional groups: The isomeric phenomena caused by the difference of functional groups mainly include:

Monoolefins and naphthenes: the general formula is CNH2N(N3) diolefins, monoalkynes and cyclomonoolefins: the general formula is CNH2N-2(N3) benzene and its homologues and polyenes:

The general formula is CNH2N-6 (N 6) saturated monool and saturated monoether: the general formula is CNH2N+2O(N2) saturated monoaldehyde, saturated monoketo, enol: the general formula is CNH2NO(N3) saturated monocarboxylic acid, saturated monoester, hydroxyaldehyde:

The general formula is CNH2NO2(N2)phenol, aromatic alcohol, aromatic ether: the general formula is CNH2N-6O(N6) glucose and fructose; Sucrose vs. maltose.

Amino acids [R-CH(NH2)-COOH] vs. nitro compounds (R'-NO2).

Don't underestimate a small organic molecular formula! A staggering number of isomers can be written in a single molecular formula!

I was trying to write all the isomers with the formula C6H6 the other day, and I still failed.

If the isomers are not required by the category, then there are: carbon frame isomerism, functional group position isomerism, functional group type (i.e., organic matter species) isomerism, stereoisomerism (some organic substances with the same structure will cause great differences in properties due to different spatial orientations). If we do not consider the complex stereoisomerism, but only consider the carbon frame isomerism and functional group position isomerism, then C8H9Cl, an isomer of halogenated hydrocarbons, should be written first, and its "unsaturation" should be calculated first

The unsaturation of C8H9Cl = [8*2+2-(9+1)] 2=4, that is, in order for the molecule to become a saturated chain halogenated hydrocarbon C8H17Cl (C8H18), it needs to add 4*2=8 hydrogen atoms.

"Unsaturation" is understood in this way: ethylene has only one double bond, then its unsaturation is 1, cyclopropane has only one carbon ring, and its unsaturation is also 1, and acetylene has one triple bond, then its unsaturation is 2).

Therefore, C8H9Cl may only contain: 4 double bonds, one triple bond, two double bonds, two triple bonds, one carbon ring, three double bonds, one carbon ring, one triple bond, one double bond, two carbon rings, two double bonds, two carbon rings, one triple bond, three carbon rings, one double bond, four carbon rings, so you have to write out the arrangement of the carbon skeleton according to all these possible cases, first it is acyclical, add three bonds, double bonds to the chain, and finally replace a chlorine atom with a different hydrogen atom; After 1 ring, 2 rings, 3 rings, 4 rings in order to try to write, note that the smallest of these carbon rings is a ternary ring, that is, three carbon atoms enclose a ring, the largest is an eight-membered ring, if it is two or more rings, then these rings may be arranged in a way that has a common point ring (such as:

Fused rings (e.g., bridging rings (e.g., the above is just an example, not C8H9Cl, and the total number of carbon atoms should be 8 and the unsaturation is not enough.

4, double or triple bonds should be added to make up for the unsaturation of the molecule, otherwise the molecular formula will not conform to C8H9Cl. You can follow this procedure to write all the organic matter with the molecular formula C8H9Cl. Of course, this is very hard, and it is easy to have heavy and leaky, so I can only tell you the way to write isomers, as for how many kinds of c8h9cl are there, hehe, the number is quite amazing!

Maybe I'm tired and can't write it all.

Of course, if the molecule contains a benzene ring, it becomes simple all of a sudden.

There are four types of high school learning.

1) Carbon chain isomerism: refers to the isomerism phenomenon caused by different carbon skeletons in molecules. For example, all alkane isomers belong to carbon chain isomerism.

2) Positional isomerism: refers to the isomerism phenomenon caused by the different positions of functional groups in the molecule. Such as l-butene and 2-butene, l-propanol and 2-propanol, o-xylene and m-xylene and paraxylene.

3) Functional group isomerism: refers to the phenomenon of isomers with the same molecular formula but different functional groups of organic matter.

4) C-trans isomerism: the isomerism caused by the different arrangement of atoms or clusters in the molecule in space due to the fact that the carbon-carbon double bond cannot be rotated. The arrangement of two identical atoms or clusters of atoms on the same side of a double bond is called cis structure; The arrangement of two identical atoms or clusters of atoms on either side of a double bond is called a trans structure.

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.

There are three structures in the organic structure of high school that are structurally unstable and do not need to be considered when writing isomers.

1. The carbon-carbon double bonds are connected together, i.e., -c=c=c-

2. The hydroxyl group is attached to the carbon-carbon double bond, that is, -c=c-oh, which will heterogeneously form a carbonyl group.

3. Multiple hydroxyl groups are attached to the same C atom, which is also called homocarbon polyol, that is, -CH(OH)2, or, -C(OH)3, etc.

A reaction to dehydration occurs.

The more branches there are, the more unstable they are.

For example, the neopentane in pentane is unstable and has 5 C's, but it is a gas. cc-c-cc thanks.

In general, knowing the molecular formula to determine the number of isomers requires only the carbon skeleton to be written, not all the connected hydrogen atoms; If the number of isomers is determined by the known structural formula, it can be represented by arrows or Arabic numerals, instead of having to write out the structural formula one by one; This saves a lot of time. To determine whether the simplified formulas of two structures are isomers of each other, we must first look at whether the molecular formulas are equal, and then see whether the structures are different.

1. Equivalent hydrogen method.

The determination of the number of primary substituents of hydrocarbons is essentially based on the number of hydrogen atoms in different positions. It can be judged by the "equivalent hydrogen method". The three principles for judging "hydrogen equivalent" are:

Hydrogen atoms on the same carbon atom are equivalent; For example, 4 hydrogen atoms in methane are equal.

Methyl groups attached to the same carbon atom are equivalent; For example, the 12 hydrogen atoms on the 4 methyl groups in neopentane are equivalent.

The hydrogen atoms in the symmetrical position are equivalent. For example, 6 hydrogen atoms in ethane are equivalent, 24 hydrogen atoms on 2,2,3,3-tetramethylbutane are equivalent, and 6 hydrogen atoms on benzene ring are equivalent.

Before determining the isomers, it is necessary to find the symmetry plane and determine the equivalent hydrogen, so as to determine the number of isomers.

2. Axis movement method.

For fused cyclic aromatic hydrocarbons with multiple benzene rings together, to determine whether they are isomers, an axis can be drawn, and then translated or flipped to determine whether they are isomers of each other.

3. Determine the method of one shift and two moves.

For the determination of isomers of binary substituents, one substituent position can be fixed and the other substituent position can be moved to determine the number of isomers.

4 Permutations and combinations.

For example, there are only two different hydrogen atoms on the naphthalene ring: a- and b-, and there are 3 cases of the combination of disubstituents: a-a: 3, a-b: 4, b-b: 3, a total of 10 isomers.

In order to help netizens solve the "college entrance examination." There are several questions about the isomers of chemical organic isomers, and the Chinese academic network has made a "college entrance examination" through the Internet. There are several how-related solutions for chemically organic isomers, and detailed user questions include:

rt, I would like to know: college entrance examination. How many isomers are there in chemical organic?

The specific solutions are as follows:

Solution 1:

When C in the branch exceeds C on the straight chain, it is denoted as one), if the structural formula conforms to the standard formula of saturated alkanes CNH2N+2, acid, ends, and is bounded by the central carbon atom of the remaining carbon chain. It can also be turned into ethyl in the same way as above.

Third, start to replace from the No. 2 position; (3) Remove two C's as substituents on the straight chain.

Two. Note that the backbone must be the longest carbon chain, all the way to the middle of the carbon atom, into ether, for example, there are several substitution methods are several isomers (when there are two C's in the center, it becomes an ester, if the structural formula conforms to unsaturated hydrocarbons (alkenes and alkynes), be careful not to repeat, the method is like step 2, just see if you can move the two oxygens. , it depends on whether the oxygen can move to the middle, these two positions are equivalent, at this time you can put 2 carbons on the same carbon to replace, starting from the 3rd position, a:

Adjacent or spaced.

Fourth, the isomerism of phenol is one, but the position of the c=c double bond is more considered. , just arrange the carbon chain, alcohol; (2) Remove a C as a substituent on the straight chain and whether it can be enough to form a naphthene: (1) First, consider that the carbon is all on a straight chain; (4) And so on.

It is also possible to separate the two carbons for substitution, which is the simplest, and consider the isomers of the esters.

Solution 2:

As for isomers, as long as you experience them carefully and explore more, you can understand them.

The former is divided into carbon-dry isomerism and functional group isomerism.

Isomers in organic are divided into conformational isomerism and conformational isomerism, and of course tautomerism can also be counted.

In high school, it is only necessary to grasp the configuration heterogeneity, which is caused by a characteristic functional group attached to different carbons.

The latter is caused by different functional groups, and the molecules are the same as the name suggests, in short, for the same class of organic matter, the different structures are isomers.

Solution 3:

Saturated alkanes, depending on the carbon skeleton has several arrangement methods, pay attention not to coincide with the previous one when moving carbon.

alcohol, it depends on whether the oxygen can be strung to the middle and become the isomer of ether. When you come into contact with phenol, you think about it.

Acid, depending on the position of the ester bond, at the end is the acid, and the outward methyl group is "methyl ester of a certain acid", to see how many methyl groups can be produced, and whether the carbon taken out is isomeric of propyl and isopropyl groups.

Solution 4:

There is no good way to do this, but to list all the possibilities and then remove the duplicates.