3.4 Alkenes

• Alkenes are unsaturated hydrocarbons that contain double bonds and have the general formula CnH2n.
• Alkenes are hydrocarbons like alkanes and contain only hydrogen and carbon.
• Alkenes are unsaturated and have one double covalent bond.
• Alkenes undergo addition reactions because of their double bonds.
• Electrophiles add to alkenes because they have a deficiency in electrons.
• Examples of electrophiles include things with a positive charge like NO2+ and H+, and polar molecules with a delta positive like HBr and SO4.
• All electrophilic addition reactions use the curly arrow to show mechanisms, starting from the double bond.
• The most electrons are in the double bond, so all electrophilic addition reactions start from the double bond.
• In an electrophilic addition reaction, the electrophile is an electron pair acceptor, and the electrons are added onto the molecule.
• Examples of electrophilic addition reactions include the addition of bromine to an alkene, which should decolorize if it's an alkene.
• Polypropylene is a type of plastic, and it is nonpolar and normally saturated due to its high number of carbons and hydrogens.
• Natural polymers include proteins and natural rubber, while synthetics are polyethylene and polypropylene.
• Alkenes are monomers, which can be joined together to form polymers through an addition polymerization process.
• Alkenes are useful for making plastics or types of polymers.
• Intermolecular forces govern the properties of polymers, just like with simple molecules.
• Polypropylene is stable and unreactive due to its high number of carbons and hydrogens, which can make it difficult for it to degrade in landfill.
• Plastics such as polyethylene, polypropylene, and Teflon have revolutionized the way we live and use plastics.
• New polymers are made all the time, including electronic gadgetry and touchscreens.
• Charles Goodyear discovered vulcanized rubber by adding chemicals to a natural rubber, making it harder wearing and ideal for tiles.
• Polypropylene can be made from monomer propane, and the double bond opens up when these monomers are joined together, forming the polymer.
• Alkenes react with cold concentrated sulfuric acid to form alkyl hydrogen sulfate.
• Hydrolysis is the process of breaking a bond using water.
• The sulfuric acid acts as a catalyst by breaking the bond between the hydrogen and the oxygen, forming a carbocation intermediate.
• The mechanism of this reaction involves the formation of an intermediate, alkyl hydrogen sulfate, which is then reformed into an alcohol using cold water.
• In the overall reaction, an alkene reacts with cold concentrated sulfuric acid to produce an alkyl hydrogen sulfate, which is then reformed into an alcohol using cold water.
• Sulfuric acid is used as a catalyst in this reaction, which produces an alcohol from an alkene.
• The sulfate or hydrogen sulfate group is negatively charged due to the loss of a hydrogen atom.
• The hydrogen atom from the water molecule adds itself onto the oxygen when it breaks off, reforming sulfuric acid and completing the catalytic cycle.
• The intermediate, alkyl hydrogen sulfate, is formed by the reaction of the double bond with the Delta positive, and the electrons move into the oxygen.
• The hydrogen atom from the double bond is bonded to the molecule, forming a carbo cation intermediate.
• Sulfuric acid is reformed in this reaction, and using asymmetric alkenes, two products can be produced.
• The bromine on the side with the delta positive is attracted to the delta positive electron pair in the double bond, breaking the bromine bond and forming a carbo cation intermediate.
• The mechanism involves the bromine molecule approaching an area with a lot of electrons like a double bond, causing electrons to shift to the opposite side of the molecule.
• Alkenes react with hydrogen halides to form halogenated alkanes.
• The color change from brown to colorless is due to the decolorization of bromine, which is a kind of bromine, to colorless because the product that is produced is colorless.
• The bromine that was left over with a lone pair then attacks the delta band at the positive carbon calf line, forming a colorless dye bromo ethane.
• The electron pair in the double bond attacks the Delta positive hydrogen, breaking the bromine bond and forming a carbo cation intermediate.
• The bromine that was left over with a lone pair then attacks the Delta band at the positive carbon calf line, forming a colorless dye bromo ethane.
• The carbo cation intermediate is a molecule formed in the middle of a full reaction.
• HBr follows the same mechanism as the addition of a halogen, with the difference being that it's polarized due to the permanent dipole created by the Delta positive and Delta negative charges.