UNSATURATED HYDROCARBONS Flashcards
a 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.
- C=C
- olefins
- 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 and propene
- diene & -triene
PHYSICAL PROPERTIES OF ALKENES AND CYCLOALKENES
- ________ in water, soluble in ________ 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 ________.
- Insoluble; nonpolar solvents
- gases
- liquids; solids
CHEMICAL REACTIONS OF ALKENES
- Combustion
- Addition reaction
- hydrogenation reaction
- halogenation
- hydrohalogenation
- hydration
symmetrical addition rx: hydrogenation & halogenation
asymmetrical addition rx: hydrohalogenation & hydration
- The combustion products are carbon dioxide and water
- _________ are, however, too expensive to be used as fuel.
- Pure alkenes
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
- a hydrogen atom is added to each carbon atom of a double bond.
- This is accomplished by heating the ______ & ______ in the presence of a catalyst (usually Ni or Pt).
- alkene and H2
HYDROGENATION REACTION
- a halogen atom is added to each carbon atom of a double bond.
___________ & ___________ are the two halogenation processes most commonly encountered.
- NO catalyst is needed.
- Chlorination (Cl2) and bromination (Br2)
- 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
_______, only one product results from hydrohalogenation.
- ethene
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 ___________ as a catalyst
- For symmetrical alkenes, only one product results from this
- H2SO4 (sulfuric acid)
HYDRATION REACTION
common names of 2 simplest alkenes
ethylene and propylene
- An acyclic unsaturated hydrocarbon that contains a carbon-carbon triple bond.
- The functional group is ________ group.
- C triple bond C
ALKYNE
- _______________, where n is the number of carbon atoms present.
- Thus, the simplest member of this type of alkyne has the formula, ______, and the next member, with n=3, has the formula ________.
- CnH2n-2
- C2H2 and C3H4
ethyne and propyne
Alkynes are _______ in water but soluble in ___________, have densities less than that of water, and have boiling points that __________ with molecular mass.
- insoluble
- organic solvents
- increase
REACTIONS OF ALKYNES
- Catalytic hydrogenation
- Halogenation
- Hydrohalogenation
- Hydration
- Oxidation
Common names for simple alkynes are based on the name _________
ACETYLENE
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
- third class of unsaturated hydrocarbons
- an unsaturated cyclic hydrocarbon that does NOT readily undergo addition reactions
AROMATIC HYDROCARBONS
- simplest aromatic hydrocarbon
- flat, symmetrical molecule with a molecular formula ______, has a structural formula that is often formalized as that of a _____________: in other words, as a structural formula that involves a six-membered carbon ring in which three double bonds are present.
- C6H6
- cyclohexatriene
BENZENE
a compound containing one or more benzene-like rings
arene
a group derived from arene by removal of a H atom from an arene and given the symbol Ar-
- not only is it poisonous if ingested in liquid form, but its vapor is also toxic and can be absorbed either by breathing or through the skin
- Long-term inhalation can cause ________ and ________
- liver damage and cancer
ARYL GROUP
a highly unsaturated carbon ring system in which both localized and delocalized bonds are present.
- In this “____________” structure for benzene, the ______ denotes the electrons associated with the double bonds that move around the ring
aromatic ring system
- circle-in-the-ring
- circle
PHYSICAL PROPERTIES OF AROMATIC HYDROCARBONS
- ________ in water, are good solvents for other _______ materials, and are less dense than water.
- Benzene, monosubstituted benzenes, and many disubstituted benzenes are _______ at room temperature.
- Benzene itself is a colorless, flammable liquid that burns with a __________ because of _____________
- Benzene: liquid at room temperature with a boiling point of about ____
- As the size or number of carbon atoms ______, the total energy of VDWs between molecules _______ and boiling points increase _______
- Insoluble; nonpolar
- liquid
- sooty flame; incomplete combustion
- 80°C
- increases
