Lab 8: Classification and Identification of Hydrocarbons

alkenes

Hydrocarbons with one or more carbon-carbon double bonds

Reaction with H2SO4

-Alkenes react with cold concentrated sulfuric acid by addition. Alkyl sulfuric acids form as products and are soluble in H2SO4. -Saturated hydrocarbons (alkanes) are unreactive (additions are not possible). -Alkynes react slowly and require a catalyst. -Aromatic are unreactive because addition reactions are difficult. **LOOK AT EQ**

Hydrocarbons

-Compounds composed of only carbon and hydrogen -Ways to classify: 1. chain hydrocarbons, depends on the way in which carbon atoms are connected. single or branched chain. 2. cyclic hydrocarbons, compounds that have carbon atoms linked in a closed polygon 3. depends on the type of bonding that exists between carbons, i.e. alkanes

Reaction with KMnO4

-Neutral dilute or alkaline solutions of KMnO4 oxidize unsaturated compounds. Product formed from an alkene is a glycol. -Alkanes and aromatic compounds are generally unreactive. -when a reaction occurs it is indicated by the loss of the purple color of KMnO4 and the formation of the brown precipitate MnO2. **LOOK AT EQ**

Saturated vs. unsaturated hydrocarbons

-Saturated molecules are hydrocarbons that contain only carbon to carbon single bonds, also called alkanes. -Unsaturated molecules are hydrocarbons containing at least one carbon to carbon triple bond, or double bond between carbon atoms.

Reaction with bromine

-Unsaturated hydrocarbons (alkenes and alkynes) react rapidly with bromine in a solution of carbon tetrachloride or cyclohexane. The reaction is the addition of the elements of bromine to the carbons of the multiple bonds. -A reaction will take place when there is a loss of color from the bromine solution and a colorless solution remains. -Because alkanes have only single C-C bonds present, no reaction is observed and the red color persists when added. -Aromatic compounds resist addition reactions, and will only react with bromine is the presence of a catalyst. **LOOK OVER EQUATIONS**

alkynes

-a carbon compound with a carbon-carbon triple bond. -referred to as unsaturated molecules

alkanes

-a hydrocarbon containing only single C-C bonds -also known as saturated molecules

aromatic

-class of hydrocarbons that contain a closed loop of electrons

When there is an oil spill in the ocean, an oil-slick develops on the surface of the water and spreads quickly. Why does this happen?

-generally hydrocarbons do not mix with the polar solvent water, but mix with relatively non polar solvents -the density is normally less than that of water, so they will float -crude oil is a mixture of hydrocarbons, so when spilled on water it spreads quickly along the surface because they are insoluble in water