Alkenes and Alkynes Flashcards
hydrocarbon in which the carbon chain or ring contains at least one carbon-carbon double bond or carbon-carbon triple bond
Unsaturated Hydrocarbons
- An acyclic unsaturated hydrocarbon that contains one or more carbon-carbon double bonds
- Alkene functional group is thus a ____________ group.
- An older but still widely used name for alkenes is _______. The term means “oil-forming”
- The ________ ending means a double bond is present.
- double bond group
- olefins = oil forming
- ene
ALKENE
- ______, where n is the number of carbon atoms present.
- Thus, alkenes with one double bond have two fewer hydrogen atoms than alkanes.
- The two simplest alkenes :
o __________ (C2H4)
o __________ (C3H6) - When two double bonds are present, the compounds are often
called _________; for three double bonds the designation _____
is used.
CnH2n
- ethene (120*)
- propene (109.5*)
- dienes
- trienes
- Insoluble in water, soluble in nonpolar solvents, and lower density than water
- Melting point is ______ than that of the alkane with the same number of carbon atoms
- Alkenes with 2 to 4 carbon atoms are ______ at room temperature.
- Unsubstituted alkenes with 5 to 17 carbon atoms and one double bond are ______, and those with still more carbon atoms are ________.
- lower
- gas
- liquid, solid
- The combustion products are carbon dioxide and water
- Pure alkenes are, however, too expensive to be used as fuel.
combustion
A chemical reaction in which atoms or groups of atoms are added to each carbon atom of a carbon-carbon multiple bond in a hydrocarbon or hydrocarbon derivative.
addition reaction
addition reactions
a. Hydrogenation Reaction
b. Halogenation Reaction
c. Hydrohalogenation Reaction
d. Hydration Reaction
- a hydrogen atom is added to each carbon atom of a double bond.
- accomplished by heating
the alkene and H2 in the presence of a catalyst (usually Ni or Pt).
Hydrogenation Reaction
- a halogen atom is added to each carbon atom of a double bond.
- Chlorination (Cl2) and bromination (Br2) are the two halogenation processes most commonly encountered
- No catalyst is needed.
Halogenation Reaction
- one carbon atom of a double bond receives a halogen atom and the other carbon atom receives a
hydrogen atom. - require no catalyst
- For symmetrical alkenes, such as
ethene, only one product results from this
Hydrohalogenation Reaction
- one carbon atom of a double bond receives a hydrogen atom and the other carbon atom receives an -OH group.
- requires a small amount of H2SO4 (sulfuric acid) as a catalyst.
- For symmetrical alkenes, only one product results from this
Hydration Reaction
Two simplest alkenes, ethene and propene, have common name.
They are _________ and __________,
respectively.
- ethylene
- propylene
- An acyclic unsaturated hydrocarbon that contains a carbon-carbon triple bond.
- The alkyne functional group is ________ group.
- The characteristic ending associated with a triple bond is -yne.
Thus, the simplest member of this type of alkyne has the formula, ______, and the next member, with n=3, has the formula ______.
alkyne
- CnH2n-2
- ethyne (acetylene): C2H2
- propyne: C3H4
- insoluble in water
- soluble in organic solvents
- have densities less than that of water
- boiling points increase with molecular mass
alkynes
Reactions of Alkyne
o Catalytic Hydrogenation
o Halogenation
o Hydrohalogenation
o Hydration
o Oxidation
Students often ask whether it is possible to have hydrocarbons in which both double and triple bonds are present.
The answer is yes.
Immediately, another question is asked.
How are such compounds named? Such compounds are called _________
alkenynes
