Regarding homologues, what are homologues

First of all, you have to figure out what a homolog is:

Many organic compounds that are structurally similar, have the same type and number of functional groups, and differ in composition by one or more CH2 clusters are called homologues.

Is the -ch2-ch2 - you wrote about a molecule? It is not a molecule, it is just a carbon chain made up of two carbons, which cannot be compared to ch2=ch2, which is ethylene.

Examples of general homologues:

Methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10) and other homologues can be expressed by the general formula CNH2N+2. Among them, methane and n-butane are homologues of each other, and methane and isobutane are also homologues of each other.

Methanol CH3OH, ethanol CH3·CH2OH, propanol CH3·CH2·CH2OH and so on are also homologues, which can be expressed by the general formula CN+H2N+1OH or ROH.

Ethylene, propylene, butene, etc. are homologues of each other, and the general formula CNH2N can be used

But organic compounds with the same chemical formula are not necessarily homologues.

For example, ethanol and ether have the general formula of CNH2N+2O, but their functional groups are different and they are not homologues.

For example, ethylene and cyclobutane have the general formula of CNH2N, but they are not homologues.

The chemical properties of a class of homologues are basically similar, and the physical properties change regularly with the increase of carbon atoms.

One of the characteristics of congeners is that two or more substances have the same functional group, and they can only differ by n CH2.

One is a monoene, the other is a diene, of course, it can't be a homologue.

Categories: Education, Science, >> Learning Aid.

Problem description: The textbook of the second year of high school says that homologues are substances with similar structures and one or several CH2 atomic clusters that differ in molecular composition from each other.

However, I also saw in the "General Review of the College Entrance Examination (Shaanxi People's Education Press)" that substances that conform to the same general formula and differ in molecular composition by one or several CH2 atomic clusters are not necessarily homologues.

What's going on? Is there a chemistry genius to help my little brother solve this problem.

Addendum: I want a true definition of a homolog.

Maybe we didn't have a comprehensive knowledge of high school and deliberately defined homologues like this.

Analysis: There is no problem with the textbook, pay attention to the sentence "similar structure", not nonsense.

There is no such sentence in the tutorial materials, so you can give a counter-example:

Acetone CH3-CO-CH3 and Propionaldehyde CH3-CH2-CHO

Question 1: What are homologues Substances with similar structures and differing by 1 or several CH2 clusters in molecular composition are called homologues to each other. Such as methane (CH4), ethane (C2H6), plant alkane (C3H8), butane (C4H10), etc., in which methane and n-butane are homologues of each other, and methane and isobutane are also homologues of each other.

Ethylene, propylene, butylene, etc. are homologues of each other.

Question 2: Definition of homologues The composition is the same, the structure is similar, and the molecular formula is different by n "-ch2-" groups.

For example, methane and ethane, propane and isobutane, and so on.

Question 3: What are homologues There are several cases 1This person is more shy.

Telling him directly will hurt him and hurt yourself 2This person is more cheerful, and it doesn't work to use a suggestive approach, and tell him directly that it's better, suggesting that such a method is only suitable for those who are shy. 3.

The personality is more withdrawn, which takes a little longer, and slowly moves with love, because he is a piece of hard ice, and you are hot water. 4.With an eccentric and moody personality, you can only break up with him or forget about this person, because such a person will cause you trouble.

Question 4: What are homologues, will be detailed, thank you Chemically, we refer to compounds with similar structures and differing in composition by 1 or several atomic clusters as homologues. It is mostly used for organic compounds.

Judgment law of homologues: One difference: the molecular composition is different by several certain atomic clusters, that is, the relative molecular mass difference is consistent, just like the tolerance in the equal difference series. Together: Same as the same type. Similar: similar in structure. [College Entrance Examination Center].

Characteristics of homologues:

1.The homologues must conform to the same general formula; However, it is not necessarily the homolog that conforms to the same general formula.

2.Congeners must be of the same class.

3.The chemical formula of the congeners must be different.

4.The constituent elements of the homologues are the same.

5.Homologues are structurally similar and not necessarily identical.

6.There are several clusters of CH2 atoms between the congeners.

Allotropes are the mutual names of different elemental substances composed of the same element; An isotope is a mutual name for different atoms of the same element with the same number of protons but different numbers of neutrons; Isomers are mutual names for compounds with the same molecular formula but different structural formulas; Homologues are substances that are structurally similar and differ in molecular composition by one or more clusters of CH2 atoms.

Differentiation of allotropes, isotopes, isomers, homologues:

1. The research objects are different.

Homologs and isomers study compounds; Allotropes study elemental matter; Isotopes are the study of atoms.

2. The structure is different.

The electron shell structure of isotopes is the same, but the structure of the nucleus is different; The elemental composition or structure of allotropes is different; The structure of the homologues is similar; The isomers of the isomers are identical.

3. The nature is different.

The physical properties of isotopes are different, and the chemical properties are the same; Allotropes have different physical properties and the same chemical properties; The physical properties of the congeners are different, and the chemical properties are similar. The physical properties of isomers are different, and the chemical properties are not necessarily the same.

4. The chemical formula is different.

The elemental symbols of isotopes are represented differently; The element symbols of allotropes represent the same, and the molecular formulas can be different; The chemical formula of the congeners is different; The chemical formula of the isomer is the same.

Homologue refers to organic compounds with similar structures and several "ch" atomic clusters with different molecular compositions; It generally occurs in organic chemistry and must be of the same class of substances (containing the same and equal number of functional groups, with the exception of hydroxyl groups, phenols and alcohols cannot be homologues, such as phenol and benzyl alcohol). However, it is worth noting that, firstly, most of the homologues differ by 1 or n methylene groups; The second is that substances with the same group are not necessarily homologues.

All linear alkanes constitute a series, the simplest member is methane, and then ethane, propane, butane, pentane, etc., their physical properties have many laws, with the increase of carbon number, the intermolecular force is enhanced, so the melting point and boiling point of alkanes are gradually increased. (Propane melting point exception).