Chemistry Teachers
Group Members
Annie Ma
George Shao
David Wu
Topic
Alkene & Alkyne
INTRODUCTION
Hydrocarbons consist of alkanes, alkenes, and alkynes.
Alkanes are single-bond, while the other two are multi-bonded.
(Double-bond alkene, triple-bond alkyne)
Alkanes are saturated hydrocarbons, while the other two are unsaturated ones.
MATERIAL
1) PPT
2) VIDEO
3) POSTER
4) EXPERIMENT
EXPLANATION OF MATERIAL
Alkene
Definition: Organic compound containing carbon-carbon double bonds
Rules for Naming
• Rules are similar as the naming of alkane
• “ane”
“ene”
• A Number
Lower numbered C
In front of parent hydrocarbon, separated by ”–”
Condensed Structure
Ex. 2-hexene
• “hex”= 6 C ( C C C C C C )
• “ene”= C=C bond
• 2
= bonds C#2~#3 ( C-C=C-C-C-C )
• C
= 4 bonds
• Count bonds between each C and its neighbours
• Subtract that # from 4
• (
=# of H attached to each C)
• (#1=4-1=3, #2=4-3=1)
• CH3-CH=CH-CH2-CH2-CH3
Geometry
• Angles are approximately 120 degrees
• 3 atoms connected to each C lie flat
• Rigid (stronger)
Physical properties
• Comparable with alkanes
• Acidity levels of alkenes are much higher than the ones in alkanes
• States depends on molecular mass
• The simplest alkenes, ethene, propene and butene are gases.
Chemical properties
• Relatively stable
• More reactive than alkanes due to the presence of a carbon–carbon pi-bond
Alkyne
Definition: Organic compound containing carbon-carbon triple bonds
Rules for Naming
• “ene”
“yne”
Condensed Structure
• The same as that of alkenes.
Geometry
• In acetylene, the H–C≡C bond angles are 180°
• Cyclic alkynes are rare.
• Benzyne is highly unstable.
• The C≡C bond distance (121 pm) is much shorter than the C=C distance in alkenes (134
pm) or the C-C bond in alkanes (153 pm).
Physical properties
• Insoluble in water, but are fairly soluble in organic solvents
• The melting and boiling points of alkynes increase with molecular mass.
Chemical properties
• Alkynes are characteristically more unsaturated than alkenes.
• Alkynes are usually more reactive than alkenes.