(Solved): Hydrocarbons are organic compounds that contain only carbon and hydrogen. Within hydrocarbons are f ...

Hydrocarbons are organic compounds that contain only carbon and hydrogen. Within hydrocarbons are four orgmnic families: 1. Alkines - all single bonds 2. Alkcnes - contains a carbon-carbon donble bond 3. Alkynes - contains a earbon-earbon triple bond 4. Arenes - aromatic. usually a derivative of benzene Hydrocarbons are sourced in the form of petroleum, natural gas, and conl tar. Initially a complex mixture, it is relined by distillation into several fractions based on boiling point ranges. One of these fractions we know very well, because it contains a mixture of hydrocarbous we use as fucl. While the bulk of the initial mixture is made up of alkanes, through processes such as "cracking" and "catalytic reforming" one can make alkenes, alkynes, and arenes as well. At this point, our modern way of life relies heavily on the nse of hydrocarbons. The average American nses several tons of petroleum each year, wliether driving to work or in purchasing conntless consumer products containing plastic made from polymerization of hydrocarbons. Several current or potential issues arise from our extensive use of hydrocarbons: - They are largely nonrenewable - Combustion of lydrocarbons (in cars, for example) result in the release of carbon dioxide, carbon monoxide, and soot - There have been several well-known socidents involving the relcase of petroleum into the environment. restulting in contumination That said. much good his come from the use of hydrocarbons as well. For example, the fine chemical industry. which supplies chemists and drug companics alike with the materials they need to discover and produce life-saving drugs, is largely based upon compounds made from hydrocarbons. Bromination Bromine reacts with alkanes, alkenes, and alkynes via addition reaction. Allous brotnination is different than allone and alkye bromination in varions ways: 1. Light is required for alkans but not for alkenes of allynes 2. When alkanes aue brominated it happens by suhstitution. wheress for alkenes and alkynes it happens. by addition 3. Bromination of alkenes and alkypes lappens immediately. whereas it tukes a while for an alkane to renct \( \mathrm{Br}_{2} \) hass a strong red-brown color wheress bromoalkmes are colotlex. Therefore, you know a reaction has happened when the solution goes from red-brown to colorhes Since the resction is much slower for nllkanes. this reaction can be used to diatinguiks nllowes from allowes and allisyus: Permanganate Oxidation Another common test for allenes and allyms involves potaseium permangannte, \( \mathrm{KMnO} \), a strong oxidant. As in the case of bromination. alkaes and arenes prove to be umreactive here. Allowes and alkyues both react, but the products formed use quite different! Alkznes react to form diols (also ealled glycols), a result that looks a lot like addition. When permanganate is combined with an alkyne, the triple bond cheaves fully, giving two products. How do we know that eitive of these reactions have occurred? One again, it's based on color. The solution of potasium jermanganate is a saturated magenta color. After the reaction. however, wo have manganese: dioxide. Manganese dioxide. MrO \( \mathrm{O}_{2} \) is brown and dissolves pootly in solution. The result is that in the ease of a successful reaction your product mixture will be bromil and brackish. Combustion All hydrocarbons react with axygen to produce carboa dioxide and water. Not all hydrocarbons have the same ratio of carbon to hydrogen, however. By definition. saturated hydrocarbots such as alkanes have the maximam number of hydrogens per carbon. When slkwas are coanbested they burn elean. Unsaturated. lydrocarbons, such as allocurs, allignes, and arenes, him fewer hylnogens per carbous yvus can imagine that unsaturated compounds have a "surplus' of carboth. As a restlt, combistion of ninsaturated hydrocaubons producen soot, and the amount of soot is proportional to the degree of unsaturation. Soot is esentially just carbon in a form that is finely divided, and therefare it floats through the wir. Becanse the amount of soot is proportional to the degree of unsaturation, soot formation can be used as a test for unsaturation. Synthesis of Acetylene In today's lab we will synthesize noefylene from calcium carbide. Calcinm carbide can be thought of as a storage form of acetylene. Acotylese is a gus at room temperature. which makes it diffieult to handle. Calcium carbide, on the other hand, is a selid. If you add calcium carbide to water (as will be done in lab) it rencts to relense acrylene. 1. What is the evideuce for the reaction of bromine? 2. What is the evidence for the reaction of potassium peruanganate with alkenes/alkynes? 3. What feature in its structural formula indicates whether a hydrocarbon is an alloane, alkene, alkytne, or arene? Show an example of each. 4. Draw chemical equations to illustrate the reaction of excess \( \mathrm{Br}_{2} \) with these organic compounds (a) Ethane (b) Ethylene: (c) Acetylene