ALIPHATIC HYDROCARBONS

• Aliphatic Hydrocarbons


  Organic compounds composed of carbon and hydrogen atoms arranged in open chains
• Alkanes


  Saturated hydrocarbons with the general formula CnH2n+2

  
• Sources of alkanes


  • The two most important natural sources are petroleum and natural gas
  • Petroleum is a complex liquid mixture of organic compounds (alkanes or cycloalkanes)
  • Natural gas consists mainly of methane (about 80%) and ethane (5% to 10%)
  • Propane is the major constituent of liquefied petroleum gas (LPG), a domestic fuel
  • Butane is the gas of choice in some areas
• Physical properties of alkanes

  • Insoluble in water because they are nonpolar
  • Occur as gases, liquids and solids depending on the number of carbons
• Classification of carbon atoms in alkanes

  • Primary (1°): a C bonded to one other carbon
  • Secondary (2°): a C bonded to two other carbons
  • Tertiary (3°): a C bonded to three other carbons
  • Quaternary (4°): a C bonded to four other carbons

  
• Reactions of alkanes


  • All the bonds are single, covalent, and nonpolar, so alkanes are relatively inert
  • Do not react with most common acids, bases, or oxidizing and reducing agents
  • Can be used as solvents for extraction or crystallization
  • React with molecular oxygen and the halogens
• Oxidation of alkanes


  1. Addition of O, removal of H

  2. Replacement of C-H bonds by C-O bonds
• Halogenation of alkanes


  One or more hydrogen atoms are replaced by halogen (X) atoms where X = F, Cl, Br, I
• Combustion of alkanes


  • The most important use of alkanes is as fuel
  • Alkanes burn to form carbon dioxide and water
  • An initiation step is required, usually ignition by a spark or flame
  • If insufficient oxygen is available, partial oxidation may occur
• Alkenes


  Unsaturated hydrocarbons with the general formula CnH2n

  
• Sources of alkenes


  • The simplest alkene, ethene or ethylene, is a plant hormone and an important starting material for the manufacture of other organic compounds
  • The alkene functional group is found in sources as varied as citrus fruits, steroids, and insect pheromones

  
• Chemicals produced from propylene (propene)


  • isopropyl alcohol
  • propylene oxide
  • cumene
  • polypropylene

  
• Physical properties of alkenes

  • Less dense than water and not very soluble in water
  • Compounds with four or fewer carbons are colorless gases, whereas higher homologs are volatile liquids
• Reaction of alkanes


  Substitution is the most common reaction
• Reaction of alkenes


  Addition is the most common reaction
• Addition of halogen to alkenes

  The halogen molecule adds across the double bond
• Hydration of alkenes


  Water adds to alkenes in the presence of an acid catalyst, forming alcohols
• Addition of alcohols to alkenes

  Alcohols react with alkenes in the presence of an acid catalyst, forming ethers
• Hydrogenation of alkenes


  Hydrogen adds to alkenes in the presence of a catalyst
• Catalytic hydrogenation of double bonds is used commercially to convert vegetable oils to margarine and other cooking fats
• Alkene hydration


  If an acid catalyst is present, water adds to alkenes. It adds as H-OH, and the products are alcohols.
• Addition of alcohols to alkenes

  1. Alcohols react with alkenes in the same way that water does. Like the addition of water, the addition of an alcohol requires an acid catalyst.

  2. The product of the reaction is an ether.
• Alkene hydrogenation


  1. The addition of hydrogen to alkenes in the presence of a catalyst.

  2. Catalytic hydrogenation of double bonds is used commercially to convert vegetable oils to margarine and other cooking fats.
• Markovnikov's rule


  When HX is added to an unsymmetrical alkene, the hydrogen becomes attached to the carbon with the most hydrogens attached to it already.
• There are only a few naturally occurring alkynes
• Alkynes


  • Alkynes and alkenes have similar physical properties.
  • Alkynes are less reactive than alkenes in electrophilic addition reactions.
  • The addition reactions of alkynes have a feature that alkenes do not have: Because the product of the addition of an electrophilic reagent to an alkyne is an alkene, a second electrophilic addition reaction can occur.
• Addition of hydrogen halides and halogens to alkynes


  1. If the alkyne is a terminal alkyne, the H+ will add to the sp carbon bonded to the hydrogen.

  2. The product of the second addition reaction is a geminal dihalide, a molecule with two halogens on the same carbon.

  
• Addition of water to alkynes

  1. Alkynes undergo the acid-catalyzed addition of water. The product of the reaction is an enol.

  2. The enol immediately rearranges to a ketone.

  
• Addition of hydrogen to alkynes

  1. Hydrogen adds to an alkyne in the presence of a metal catalyst such as palladium, platinum, or nickel in the same manner that it adds to an alkene.

  2. The product of the hydrogenation reaction is an alkane.
• Valproic acid


  used to treat seizure disorders, mental/mood conditions (such as manic phase of bipolar disorder)

  
• Amobarbital


  sedative-hypnotic

  
• Phencyclidine

  • also known as angel dust
  • dissociative hallucinogenic drug used for its mind-altering effects

  
• Ethosuximide

  • used to control absence seizures (petit mal)

  
• Secobarbital


  anesthetic, anticonvulsant, anxiolytic, sedative, and hypnotic

  
• Diethylstilbestrol

  • a synthetic, nonsteroidal form of estrogen
  • well-known teratogen and carcinogen

  
• Vinyl chloride


  manufacture of poly (vinyl chloride)—PVC

  
• Stilbene


  manufacture of dyes and optical brighteners, and also as a phosphor (luminescence) and a scintillator

  
• Allylisopropylacetamide


  acts as a suicide inactivator of CYTOCHROME P450 by covalently binding to its heme moiety or surrounding protein.

  
• Fluroxene


  is a volatile, inhalational anesthetic, and was the first halogenated hydrocarbon anesthetic to be introduced.

  
• Ponatinib


  Oral drug developed by ARIAD Pharmaceuticals for the treatment of chronic myeloid leukemia (CML).