Unsaturated Hydrocarbons

alkenes and alkynes

-alkenes and alkynes are 2 families of organic molecules that contain multiple bonds. -because alkenes and alkynes are composed of nonpolar C-C and C-H bonds, their physical properties are similar to other hydrocarbons. -alkenes and alkynes have low mp and bp and are insoluble in water. -acyclic alkanes are saturated hydrocarbons; alkenes and alkynes are unsaturated hydrocarbons. -alkanes are saturated hydrocarbons because they contain the maximum # of H atoms per C. -the multiple bonds of an alkene or alkyne is always drawn in a condensed structure. To translate a condensed structure to a complete structure with all bond lines drawn in, make sure that each C of a double bond has 3 atoms around it, and each C of a triple bond has 2 atoms around it.

unsaturated vegetable oil

2 C=C's; lower mp; liquid at rm. temp.

compounds that contain C-C multiple bonds

alkenes, alkynes, and aromatic hydrocarbons.

fatty acids

are carboxylic acids (RCOOH) with long carbon chains of 12-20 C atoms. -because a fatty acid has many nonpolar C-C and C-H bonds and few polar bonds, they are insoluble in water. -2 types of fatty acids: saturated and unsaturated.

double bonds

are composed of 1 strong and 1 weak bond.

unsaturated hydrocarbons

are compounds that contain fewer than the maximum # of hydrogen atoms per carbon.

polymers

are large molecules made up of repeating units of smaller molecules, called monomers, covalently bonded together. -include the naturally occurring proteins that compose hair, tendons, and fingernails. They also include such industrially important plastics. -to form a polymer from an alkene monomer, the weak bond that joins the 2 carbons of the double bond is broken and new strong C-C single bonds join the monomers together. -ex. joining ethylene monomers together forms the polymer polyethylene. -do not readily degrade.

oils

are liquids at rm. temp.; are generally formed from fatty acids having a larger # double bonds. -when an oil is partially hydrogenated, some double bonds react with H2, while some double bonds remain in the product. Since the product has fewer bonds, it has a higher mp. Thus, a liquid oil is converted to a semi-solid.

fats and oils

are organic molecules synthesized in plant and animal cells from fatty acids. -fats and oils have different properties.

fats

are solids at rm. temp. Fats are generally formed from fatty acids having few double bonds.

alkynes

compounds that contain a C-C double bond. -the general molecular formula for an alkyne is CnH2n-2, so an alkyne has 4 fewer H's than an acyclic alkane. -acetylene (C2H2), aka ethyne [IUPAC], is the simplest alkyne. Each C of acetylene is surrounded by 2 atoms, making each C linear with bond angles of 180°. -identified by the suffix '-yne'. [IUPAC].

alkenes

compounds that contain a C-C double bond. -the general molecular formula of an alkene is CnH2n, so an alkene has 2 fewer hydrogens than an acyclic alkane, which has a general molecular formula of CnH2n+2. -ethylene (C2H4), aka ethene [IUPAC], is the simplest alkene. -since each carbon of ethylene is surrounded by 3 atoms, each C is trigonal planar. All 6 atoms of ethylene lie in the same plane, and all bond angles are 120°. -identified by the suffix '-ene'. [IUPAC]. -reactions of alkenes: hydrogenation and hydration. -undergo addition reactions; new groups X and Y are added to a starting material. 1 bond of the double bond is broken and 2 new single bonds are formed.

phenols

compounds that contain a hydroxyl group bonded to a benzene ring. -occur in nature. -ex. vanillin and curcumin. -many are antioxidants, compounds that prevent unwanted oxidation reactions from occurring. -ex. naturally occurring vitamin E and synthetic BHT. -the OH group on the benzene ring is the key functional group that prevents oxidation reactions from taking place. -vitamin E is a natural antioxidant found in fish oil, peanut oil, wheat germ, and leafy greens; helps retard the aging process by preventing unwanted oxidation reactions of unsaturated fatty acid residues in cell membranes to occur. -synthetic BHT, butylated hydroxy toluene, are added to packaged and prepared foods to prevent oxidation and spoilage; common additive in cereal.

aromatic hydrocarbons

contain a benzene ring, a six-membered ring with 3 double bonds.

constitutional isomer

differ in the way the atoms are bonded to each other. -cis and trans are isomers, but not constitutional isomers. -constitutional isomers are possible for alkenes of a given molecular formula. -ex. there are 3 constitutional isomers for an alkene of molecular formula C4H8: 1-butene (CH2=CHCH2CH3), 2-butene (CH3CH=CHCH3), and 2-methylpropene (CH2=CCH3-[CH3]). -there is restricted rotation around the C atoms of a double bond. As a result, the groups on one side of the double bond cannot rotate to the other side. -with 2-butene, there are 2 ways to arrange the atoms on the double bond: they can be on the same side, or opposite sides. These molecules are different compounds with the same molecular formula.

isomers

different compounds with the same molecular formula. -3 types of isomers: cis, trans, and stereo. -the cis and trans isomers of 2-butene are a specific example of a general class of isomer that occurs at C-C double bonds. Whenever the 2 groups on each end of a C=C are different from each other, 2 isomers are possible.

polysubstituted benzenes

for 3 or more substituents on a benzene ring: 1. # to give the lowest possible #s around the ring. 2. alphabetize the substituent names. 3. when substituents are part of common roots, name the molecule as a derivative of that monosubstituted benzene. The substituent that comprises the common root is located at C1, but the "1" is omitted from the name.

unsaturated fatty acids

have 1 or more double bonds in their long hydrocarbon chains. -oleic and linoleic acids are the most common unsaturated fatty acids. -generally, double bonds in naturally occurring fatty acids are cis. -the presence of cis double bonds affects the mp greatly; as the # of double bonds in the fatty acid increase, the mp decreases. -are common in vegetable sources. -ex. olive oil and safflower oil.

saturated fatty acids

have no double bonds in their long hydrocarbon chains. -stearic acid is 1 of the 2 most common saturated fatty acids. -are typically obtained from animal sources. -ex. butter and lard; exception coconut oil. -high levels bad for you, linked to heart disease, as well as trans fat.

addition reaction

is a reaction in which elements are added to a compound. -the weak bond in a double bond is broken and 2 strong bonds are formed.

hydrogenation

is the addition of hydrogen (H2) to an alkene. -2 bonds are broken, 1 bond of the C-C double bond and the H-H bond, and 2 new C-H bonds are formed. -the addition of H2 only occurs in the presence of a metal catalyst, such as palladium (Pd). -Pd provides a surface that binds the alkene and H2, which speeds up the reaction. -hydrogenation of an alkene forms an alkane. -1 addition reaction of alkenes, hydrogenation, is especially important in the food industry. -during hydrogenation, some of the cis double bonds in vegetable oils are converted to trans double bonds, forming so-called "trans fats".

stereoisomer

isomers that differ only in the 3-D arrangement of atoms. -cis and trans are a type of stereoisomer. -differ only in the 3-dimensional arrangement of atoms.

saturated vegetable oil

margarine; 1 C=C; higher mp; semi-solid at rm. temp.

aromatic compounds

represent another type of unsaturated hydrocarbons. -aromatic refers to compounds that contain a benzene ring, or rings that react in a similar fashion. -benzene is the simplest aromatic compound, contains a 6-membered ring and 3 double bonds. -each C of the ring is bonded to a H atom, C6H6, is trigonal planar, planar molecule, and bond angles are 120°. -low mp and bp and water insoluble. -monosubstituted benzenes: toluene(CH3), phenol(OH), aniline(NH2). -3 different ways that 2 groups can be attached to a benzene ring, prefixes ortho(2), meta(3), or para(4), is used to designate the relative position of the 2 substituents.

hydration

the addition of water to an alkene. -2 bonds are broken, 1 bond of the C-C double bond and the H-OH bond, and new C-H and C-OH bonds are formed. -only occurs if a strong acid, such as H2SO4, is added to the reaction mixture. -the product is alcohol. -ex. the hydration of ethylene is ethanol. -in the addition of H2O to an unsymmetrical alkene, the H atom bonds to the less substituted C atom, that is, the C that has more H's to begin with.

polymerization

the joining together of monomers to make polymers.-many ethylene derivatives having the general structure CH2=CHZ are also used as monomers for polymerization.

trans isomer

when the 2 CH3 compounds are on opposite sides of the double bond. -the other isomer is called trans-2-butene.

cis isomer

when the 2 CH3 groups are on the same side of the double bond. -1 isomer of 2-butene is called cis-2-butene.