Organic chemistry tutorials advanced level | High School

In this tutorial, first we present different organic compounds and then discuss about basics of organic chemistry.

Examples

Methane

You can see, only one carbon and four hydrogen atoms include in methane molecule. Four hydrogen atoms are bonded to carbon by single bonds.

Ethanol

Carbon, hydrogen and oxygen include in ethanol. Ethanol has different physical and chemical properties than methane. Ethanol react with Na, but methane doesn't.

Hydrocarbons

Halogen derivatives organic compounds

Oxygen derivatives of organic compounds

Nitrogen derivatives of organic compounds

Organic conversions

Preparing special organic compounds

Important Reactions

Common factors of organic chemistry

Problems

Organic Chemistry Introduction

Covalent bonds of carbon

Carbon takes the noble gas configuration only by sharing electrons with other atoms and it forms covalent bonds. Therefore, a carbon atom forms four covalent bonds in its compounds. As a example, carbon atom in the methane molecule share its four electrons with four hydrogen atoms to form four covalent bonds.

Methane molecule and covalent bonds

Structures and molecular formula

We can represent organic molecule in different ways. If we want to represent ethane(contains two carbon atoms and six hydrogen atoms) molecule we can draw its structure or give number of carbon and hydrogen atoms includes in the molecule such as C₂H₆ or CH₃CH₃.

Ethane structure and molecular formula

There are two carbon atoms and six hydrogen atoms in ethene molecule. A single bond exists between two carbon atoms and three hydrogen atoms are attached to one carbon atom. Molecular formula of ethane can be written as C₂H₆.

Representing covalent bonds

To represent covalent bonds, straight lines are used. For representing
single bond > one straight line (C-C)
double bond > two straight lines parallelly (C=C)
double bond > two straight lines parallelly (C≡C)

Isomerism

Isomerism are defined as having same molecular formula but their structures are different. There are two isomerism types as structural isomerism and stereoisomerism.

Structure and properties of organic compounds

Physical and chemical properties depend on the structure of the molecule. As a example, we can consider molecular formula C₂H₆O, to understand this change. C₆H₆ can be ethanol or dimethyl ether.

Ethanol and dimethyl ether

Dimethyl ether is a gas in room temperature. Also it does not react with Na. But in room temperature, ethanol is a liquid and reacts with Na to emit H₂.

Qualitative analysis of organic compounds

The qualitative analysis of an organic compound involves the detection of all the elements present in the organic compound. Oxygen, nitrogen, sulfur, halogens, phosphorus also present in some compounds. Some examples are shown below.

• Oxygen derivative compounds : ethanol, ethanoic acid, phenol
• Nitrogen derivative compound : Benzene diazonium salt, Ethanamide
• Halogen derivative compound : Chlorobenzene

Identify carbon and hydrogen

Organic compound and cupric oxide(CuO) is mixed and heated(burnt). Products are sent through anhydrous copper sulfate(CuSO₄) and lime water( Ca(OH)_2(aq) ).

1. Anhydrous CuSO₄ is turned to blue by water. Water is formed by the oxidizing of hydrogen in the organic compound.
2. Ca(OH)_2(aq) is turned to milky by CO₂. Carbon in the organic compound is oxidized into CO₂.

This method is called as copper oxide test. If organic compound is volatile liquid or gas, then vapour should be sent through heated CuO and the liberated gases are tested for CO₂ and water.

Detection of nitrogen

Nitrogen in organic can be tested by two methods.

Soda lime test

A pinch of organic compound is heated strongly with soda lime (NaOH + CaO) in a test tube. If NH₃ gas evolves, it indicates nitrogen.

Detection of sulphur

Sulphur is an organic compounds can be detected by Lassaigne's test. Sodium extract or Lassaigne solution is used to identify sulphur. The sulphur in the compound reacts with sodium metal to form sodium sulphide (Na₂S).

Now The Lassaigne's extract is tested in two parts for following tests.

Bonds and polarity

Polarity is a very important concept when we discuss about properties and structure. We know electrons of the bond are attracted towards the more electronegative atom. Then more electronegative atom of the bond holds a partial negative charge(δ-) and other atom has a partial positive charge(δ+).

Polarity of chloromethane

Chloromethane is a alkyl halide compound. We know electronegativity of chlorine is higher than carbon. Therefore, chlorine receives a δ- charge and carbon receives a δ+ charge.

Polarity of molecule has effects on melting points, boiling points, solubility and more.

Reactions

Organic compounds show different types of reactions. Reaction types are decides by the mechanism of reaction or how the reaction happens.

• Addition reactions
• Substitute reactions
• Elimination reaction
• Rearranging reactions

Examples of organic reactions

• Addition of Br₂ to alkenes
• Alcohol and Na reaction
• Benzene nitrosation

Mechanisms of reactions of organic chemistry

A description of changes occurred in a reaction forming products by reactants is defined as a mechanism of reaction. Important points of mechanism of reaction can be gained by experiments.

What we study in mechanism of reaction?

1. Number of steps in the complete reaction
2. Changes of bonds and bonding
3. Energy changes occurred while changing bonding

Single step reaction

All changes of bonds are occurred in a single step.

Multi step reaction

Reactants are converted into intermediate products first. These intermediate products are unstable and quickly participate to the next steps of reaction and give final products.

Organic chemistry questions and answers

How many organic compounds were found?

More than one million compounds were found so far.

Why organic chemistry is so important?

In human body contains organic compounds. To explain biochemistry, organic chemistry is used. Also chemistry of food, medicines, textiles, plastic has a significance effect of organic chemistry.

Should include hydrogen in all organic compounds?

No. There are some organic compounds without hydrogen. CCl₄ is an example.

Is carbon tetrachloride is a organic compound?

Yes.

How identify occurrence of nitrogen and halogens in organic compounds?

Organic compounds are converted into inorganic compounds using lassaigne's test. Then, testing inorganic anions will tell occurrence of nitrogen and halogens.

For what elements, Lassaigne's test can be used?

Lassaigne's test can be used to identify nitrogen, halogens, sulfur in organic compounds.

What are the hydrocarbons?

The compounds which contain only carbon and hydrogen are defined as hydrocarbons. They are represent by C_xH_y and x, y are positive integers.

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