Презентация по алкенам на английском

1. Alkenes
Khatskevich Katya

2. Formulae
Alkenes are a family of hydrocarbons (compounds containing carbon and
hydrogen only) containing a carbon-carbon double bond.
The simplest alkene is ethene (C2H4).
We can work out the formula of any of alkene CnH2n

3. Structural isomerism
All the alkenes with 4 or more carbon atoms in them show structural isomerism.
This means that there are two or more different structural formulae that we can draw
for each molecular formula
For example, with C4H8, it isn't too difficult to come up with these three structural
isomers:
There is, however, another isomer. But-2-ene also exhibits geometric isomerism.

4. Geometric (cis-trans) isomerism
It is an example of stereoisomerism; found in some, but not all, alkenes. Occurs due to
the restricted rotation of C=C bonds and get two forms:
1) CIS(Z) – groups/atoms are on the same side of the double bond
2) TRANS(E) – groups/atoms are on opposite sides across the double bond

5. Physical state: Alkenes with 1-4 Carbon atoms are gases
Alkenes with 5-7 Carbon atoms are volatile liquids
Alkenes with more than 18 Carbon atoms are solids
Melting and Boiling Point: Alkenes usually have low melting and boiling points
Solubility: Alkenes are virtually insoluble in water, but dissolve in organic solvents

6. Common Addition Reactions of Alkenes
1. These addition reactions include catalytic
hydrogenation, halogenation and
hydrohalogenation
2. Alkenes undergo diverse cycloaddition
reactions to give cyclohexenes.
Oxidation reactions
Oxidation of alkynes by strong oxidizing agents
such as potassium permanganate or ozone will
yield a pair of carboxylic acids. The general
reaction can be pictured as:
Combustion reactions
When burnt in air or oxygen, alkenes form carbon
dioxide and water. The reaction is highly
exothermic in nature and the heat evolved is used
for welding purposes.

7. Ethene and propene are present in small quantities in natural gas and petroleum and used to
manufacture plastics and a number of organic chemicals, including ethanol, acetic acid, and
ethylene glycol .

8. In this presentation, we looked at all the main
characteristics of alkenes and their properties.
Thanks for your attention
Khatskevich Katya