Organic chemistry can be considered as an important theoretical part, playing a central role in the general chemistry curriculum. Types of exercises about organic chemistry almost half of all the tests. To help them consolidate the knowledge they have learned about organic chemistrylet’s read the article below with hkmobile.vn team.
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Definition of organic compounds
Organic compounds are defined as compounds of carbon (except those such as CO2CO, carbonate salts and compounds of cyanide and carbides, etc.).
Features of organic compounds
To be recognized as an organic compound, the compound in question must meet the following criteria:
- The composition must contain C.
- The C atoms must bond with each other and have bonds with H, O, N, etc.
- Chemical bonds are mainly covalent bonds.
- Less thermally stable, more flammable than inorganic, volatile compounds.
- The reactions take place often slowly, not completely or not in a certain direction to form many products.
- Most are insoluble in water, only sparingly soluble in organic solvents.
Classification of organic compounds
Program organic chemistry in high school will also help them know how to classify organic compounds. As follows:
- Organic compounds are generally divided into two categories:
- Hydrocarbon: in a compound molecule containing only 2 elements, C and H. Hydrocarbons will be divided into types: saturated hydrocarbons (alkanes, …), unsaturated hydrocarbons (alkenes, alkynes, …), aromatic hydrocarbons (benzene, … )
- Derivatives of hydrocarbons: are compounds in which, in addition to C and H, there are other elements such as O, N, S, Cl, etc. Hydrocarbon derivatives are also divided into many types such as halogen derivatives (CH).3Cl, C6H5Br…); alcohol (ONLY3OH, C2H5OH,…);…
- Besides, people also classify organic compounds based on the form of carbon chain:
- Open chain: the molecular structure of organic compounds does not close into a closed loop, including straight chains and branched chains.
- Cyclic: Organic compounds have the structural formula in the form of a closed ring, including co-ring (the ring consists of only C) and heterocyclic (in addition to C, it also contains other chemical elements such as O, N, … on the ring). ).
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Names of organic compounds
To be able to identify well the compounds commonly found in organic chemistryyou need to know the rules for naming these compounds.
Common names
The common names of organic compounds are often given based on the source of the discovery of these substances.
For example:
- HCOOH: formic acid (formica: ant).
- ONLY3COOH: acetic acid (acetus: vinegar).
IUPAC nomenclature
According to IUPAC nomenclature, we will have the formula to name organic compounds as follows:
- Original name: Original part name + title part name.
- ONLY3ONLY2Cl: ethyl chloride
- ONLY3COOCH2ONLY3: ethyl acetate
- ONLY3ONLY2-O-ONLY3: ethyl methyl ether
- Alternative name: Alternative part name + main C circuit name + designation part name
- ONLY3ONLY2Cl: chlorethane
- ONLY2= ONLY2: ethene
- ONLY2=CH-ONLY2– ONLY3: but-1-en
In addition, to be able to easily name organic compounds, students need to memorize the following formula table:
| Cardinal number | Name | Main Carbon Circuit | Name |
| first | mono | OLD | meter |
| 2 | Go | CC | et |
| 3 | tri | CCC | prop |
| 4 | tetra | CCCC | but |
| 5 | penta | CCCCC | pent |
| 6 | hexa | CCCCC | hex |
| 7 | hepta | CCCCCCC | hep |
| 8 | octa | CCCCCCCC | oct |
| 9 | nona | CCCCCCCCC | non |
| ten | deca | CCCCCCCCCC | dec |
Elemental analysis in organic chemistry
In the program organic chemistry High school will have 2 ways to analyze chemical elements as follows:
Qualitative analysis
- Purpose: Determine the element present in a known organic compound.
- Principle: Convert organic elements in compounds into simple inorganic substances. Then use the characteristic responses to identify.
Quantitative analysis
- Purpose: Determine the composition % by mass of elements present in organic compounds.
- Principle: Determine the exact mass of the organic compound to be analyzed. Next, convert element C to CO2H becomes HUE2O, N to N2. Finally, calculate the exact mass or volume of the substances formed. From this, calculate the original mass % of the elements.
Molecular formula of an organic compound
To be able to do well in all kinds of exercises about organic chemistrythe molecular formula of these compounds is one of the important knowledge that students need to master.
General formula
General formulas will help children know about the elements in organic compounds. For example, with the general formula CxHyOzNt, we will confirm that in this organic compound there are elements C, H, O and N.
The simplest recipe
The simplest formula is defined as a formula that represents in minimum the ratio of the number of atoms present in a given organic compound.
To establish a simple formula for the organic compound CxHyOzNt, we rely on the ratio:
\begin{aligned}
&\bull x:y:z:t=\frac{m_C}{12}=\frac{m_H}{1}=\frac{m_O}{16}=\frac{m_N}{14}\\
&\bull x:y:z:t=\frac{\%m_C}{12}=\frac{\%m_H}{1}=\frac{\%m_O}{16}=\frac{\%m_N}{14}
\end{aligned}
Molecular Formula
Molecular formula is a formula that expresses the number of atoms of each element present in a molecule.
To establish the molecular formula, you can apply one of three ways as follows:
Method 1: Based on the composition % by mass of elements
Given the molecular formula CxHyOzwe will have the ratio:
\frac{M}{100}=\frac{12.x}{\%m_C}=\frac{1.y}{\%m_H}=\frac{16.z}{\%m_O}
From there we have:
\begin{aligned}
&\circ x=\frac{M.\%m_C}{12.100}\\
&\circ y=\frac{M.\%m_H}{1.100}\\
&\circ z=\frac{M.\%m_O}{16.100}
\end{aligned}
Method 2: Based on the simplest formula
B1: Call the molecular formula of the organic compound:n (with nN)
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B2: Calculate the unsaturation (k) of the molecule (only applicable when the compound contains covalent bonds, not to compounds with ionic bonds).
B3: Based on the expression k to choose the value n. From this, we will deduce the molecular formula of the organic compound.
- Suppose an organic compound has the molecular formula C .xHyOzWOMENt then the total number of links? and the ring of a molecule is called the unsaturation of that molecule.
- Formula to calculate unsaturation (k):
\begin{aligned}
&k=\frac{2x+2+t-y}{2}\text{ (k: tổng số liên kết }\pi \text{ và vòng)}\\
&y=2x+2+t-2k
\end{aligned}
Method 3: Direct calculation based on information about the volume of combustion products
For combustion reaction:
C_xH_yO_zN_t + \left(x+\frac y4–\ \frac z2\right) O_2 → xCO_2 + \frac y2H_2O + \frac t2 N_2
- Apply the principle of conservation of elements: nOLD= nCO2; nH= 2.nH2O; nWOMEN= 2.nN2
- Apply the principle of conservation of mass: mHCHC = mOLD + mH + mO + mWOMEN + … = total mass of elements.
Combustion products of organic compounds (CO2H2O,…) is absorbed into the flasks:
- The absorbents are H2SO4 solid, P2O5anhydrous salts → the volume of the flask increases is the volume of water;
- Basic solutions are often used to absorb CO .2we can deduce that the increasing average mass is the mass of CO2
If you encounter problems for mixtures of combustion products (CO2 and THEY2O) into a container of clear lime water or Ba(OH) solution.2 then:
- Volume of tank increased: m↑= mCO2+ mH2O
- The volume of solution increases: mdd↑= (mCO2+ mH2O) – mPrecipitation
- Volume of solution reduced: mdd↓= mPrecipitation – (mCO2+ mH2O)
Structural formulas of organic compounds
The theory of chemical structure in organic chemistry refers to some important knowledge to know as follows:
- In the molecule of organic matter, the atoms will bond with each other according to the same valence and in a certain order. This bond order will be called the chemical conformation.
- Changing the bond order will form new organic compounds.
- The properties of these compounds will be determined based on the molecular composition and chemical structure of the substance.
The phenomenon of homology and isomerism
Equivalence and isomerism are also two basic concepts that students need to distinguish when learning organic chemistry.
Peer
Homologous refers to substances with similar chemical properties but less than one or more groups – ONLY2.
Example: methane ONLY4ethane C2H6propane C3H8 are equivalents of each other.
Isomers
The concept of isomers is used to refer to compounds with the same molecular formula but different chemical structures.
Example: The formula is C2H6O will have 2 structural formulas:
ONLY3 – ONLY2 – OH (ethyl alcohol) and CH3 – O – ONLY3 (dimethyl ether).
Classification of bonds in organic compounds
In organic compounds, the common types of bonds are as follows:
- A bond formed by a shared pair of electrons is called a single bond, which is a σ bond. A single bond is represented by two dots or a hyphen between two atoms.
- The bond formed by 2 shared electron pairs is a double bond, consisting of 1 σ bond and 1 ? bond, represented by 4 dots or 2 hyphens.
- The bond formed by 3 shared electron pairs is a triple bond, consisting of 1 σ bond and 2 ? bonds, represented by 6 dots or 3 hyphens.
- Double bonds and triple bonds are collectively known as multiple bonds.
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Organic chemistry contains a lot of important knowledge for high school students. Hopefully after reading the article, they will know more useful and new information about organic compounds. I hope you have a great time with your classes and get the results you want.
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