Lab 6: Classification and Identification of Hydrocarbons

What are hydrocarbons?

consist of only carbon and hydrogens, but their connectivity can vary

What are the three different categories of hydrocarbon?

saturated, unsaturated, and aromatic

What are saturated hydrocarbons?

only sigma bonds, chemically inert, single bonds

What are unsaturated hydrocarbons?

sigma and pi bonds, addition reaction, double or triple bonds

What are aromatic hydrocarbons?

sigma and delocalized pi bonds, undergo substitution reaction in presence of a catalyst

How do unsaturated hydrocarbons react with bromine?

rapidly and red solution will go colorless

Because alkanes only have sigma bonds, what reaction is observed?

no reaction, red solution will persist

What do aromatic compounds do?

resist addition reactions

However, when would an aromatic compound react?

if iron fillings or zinc chloride are present

How do unsaturated hydrocarbons react with potassium permanganate?

compounds are oxidized

How do alkanes and aromatics react with potassium permanganate?

generally unreactive

What is the evidence of a reaction with potassium permanganate?

loss of a purple color and formation of brown precipitate (manganese dioxide)

How do alkenes react with concentrated sulfuric acid (H2SO4)?

will react through addition

How do saturated and aromatic compounds react with concentrated sulfuric acid (H2SO4)?

unreactive

What are the five hydrocarbons used in the physical properties test?

hexane, cyclohexene, toluene, unknown #1 and #2

What is added to the test tubes in the water solubility of hydrocarbons test?

5 drops of hydrocarbon into their respective test tube, and 5 drops of water

What is added to the test tubes for the solubility of hydrocarbons in the petroleum ether test?

5 drops of hydrocarbon into their respective test tube, and 5 drops of petroleum ether

What type of solvent is petroleum ether?

nonpolar

What type of solvent is water?

polar

What are the results of the petroleum ether test compared to?

the water test

What is added to the test tubes for the chemical properties and reaction with the Br2 test?

5 drops of hydrocarbon into their respective test tube, 1% Br dropwise till colorless

How many drops should you not exceed when doing the reaction with Br2 test?

no more than 10

What should you do if the red color still persists in the reaction with Br2 test?

add 5 more drops of Br solution and small amount of ZnCl2

What is the final step of the reaction with the Br2 test?

hold blue pH paper above the surface of liquid

What is added to the test tubes for the chemical properties and reaction with potassium permanganate?

5 drops of hydrocarbon into their respective test tube, and 1% neutral KMnO4 dropwise until brown

In the reaction with the concentrated sulfuric acid test, what must be done after adding the hydrocarbon drops?

place all test tubes in ice bath

What is added to the test tubes for the chemical properties and reaction with concentrated sulfuric acid?

5 drops of hydrocarbon into their respective test tube, and 3 drops of cold H2SO4 to each (in ice bath), shake

How do you know if a reaction has occurred in the concentrated sulfuric acid test?

if heat evolves, color produced, if it's homogenous

What are the hazards of the organic compounds used in this lab?

flammable and toxic

What are the hazards of bromine used in this lab?

toxic and corrosive

What are the hazards of potassium permanganate used in this lab?

toxic

What are the hazards of concentrated sulfuric acid used in this lab?

corrosive

If you get anything on your skin, what should you do?

flush thoroughly with water

What is being tested in the physical properties test portion of this lab?

solubility in water and petroleum ether

What is being tested in the chemical properties test portion of this lab?

reaction with bromine, potassium permanganate, and concentrated sulfuric acid