Intro to Organic Chemistry

History and Definition

• Organic chemistry studies carbon-containing compounds and stands as a major branch of chemistry.
• Ancient people extracted chemicals for medicine without formally calling it "organic chemistry."
• Willow bark's pain-killing properties were known, due to acetylsalicylic acid, the active ingredient in aspirin.
• Modern pharmacology is rooted in the knowledge of organic chemistry.
• Jon Jacob Berzelius defined organic chemistry in the early 1800s.
• He classified compounds as organic if from living matter and inorganic if from minerals.
• Berzelius believed in Vitalism, where organic compounds came only from living organisms via a vital force.
• Frederich Wöhler, a student of Berzelius, disproved Vitalism in 1828.
• Wöhler synthesized urea, an organic compound, by heating ammonium cyanate, an inorganic compound.
• Wöhler's synthesis was a turning point, disproving Vitalism and showing organic compounds can come from inorganic sources.
• Wöhler's work led to the discovery of isomerism with ammonium cyanate and urea, both having the formula N2H4CO.
• August Kekulé and Archibald Scott Couper developed the theory of chemical structure in 1858.
• By the 1860s, chemists proposed theories about the relationship between a compound's chemical formula and its atomic arrangement.
• By the 1900s the focus shifted to understanding chemical bonding using electron distribution models.
• Organic chemistry expanded into polymer chemistry, pharmacology, bioengineering, and petro-chemistry in the 20th century.
• Today, over 98% of known compounds are organic.

Matter and Organic Compounds

• Sources of organic compounds are carbonized organic matter, living organisms, and human ingenuity.
• Matter is anything with mass that occupies space.
• Organic compounds are composed of hydrogen, oxygen, and carbon as well as other derivatives
• Organic compounds are characterized by the presence of carbon atoms
• Organic compounds are said to be highly inflammable

Aliphatic Compounds and Hydrocarbons

• An aliphatic compound contains hydrogen and carbon atoms linked in straight chains.
• "Aliphatic" comes from the Greek word "Aleiphar," which means "fat."
• Hydrocarbons have only carbon and hydrogen.
• Hydrocarbons are divided into aliphatic and aromatic types.
• Aliphatic hydrocarbons consist of chains of carbon atoms.
• Alkanes are aliphatic hydrocarbons with single covalent bonds.
• Alkenes have at least one C–C double bond.
• Alkynes have a C–C triple bond.
• Cycloalkanes (or cycloalkenes or cycloalkynes) are aliphatic hydrocarbons with a ring of carbon atoms..
• Alkanes are saturated hydrocarbons with the maximum possible number of hydrogen atoms.
• Alkanes, alkenes, alkynes, and cycloalkanes are hydrocarbons with only carbon and hydrogen.
• They form homologous series where members differ by a CH2 unit.
• The simplest alkanes have straight chains of carbon atoms which are known as normal alkanes.

Alkanes, Alkenes, and Alkynes

• The smallest alkane is methane.
• Methane has a three-dimensional structure, with H atoms at the corners of a tetrahedron.
• Structural formulas show a molecule's structure.
• Condensed structural formulas list hydrogen atoms next to their carbon atoms.
• Line-angle formulas imply carbon atoms at corners and ends of lines.
• Each carbon atom forms four bonds.
• Methane (CH4), ethane (C2H6), and propane (C3H8) begin a homologous series differing by a CH2 unit.
• The general formula for alkanes is CnH2n + 2.
• An alkane with eight carbon atoms has the formula C8H18.
• IUPAC (International Union of Pure and Applied Chemistry) nomenclature is a system for naming hydrocarbons.
• The stem name indicates the number of carbons in the longest continuous chain (LCC).
• Substituents are named with numbers indicating their positions.
• A straight chain of carbon atoms is often called a straight chain due to the tetrahedral arrangement
• Straight-chain alkanes are sometimes called normal alkanes, with the prefix "n-."
• Alkenes are unsaturated compounds containing one or more double bonds.
• Alkynes are unsaturated compounds containing one or more triple bonds.
• An unsaturated hydrocarbon contains less than the maximum amount of hydrogen atoms possible.
• A double bond consists of one sigma (σ) bond and one pi (π) bond.
• A triple bond consists of one sigma (σ) bond and two pi (π) bonds.
• Differing geometries are responsible for the different properties of unsaturated versus saturated fats and oils.
• Ethene (C2H4), or ethylene, is the simplest alkene with a trigonal planar structure.
• Ethyne (C2H2), or acetylene, is the simplest alkyne.
• Carbons in a triple bond have bond angles of 180°, leading to a linear shape.
• The IUPAC nomenclature for alkynes uses the suffix "-yne" to indicate a triple bond.

Naming and Properties

• When naming alkenes and alkynes, the longest carbon chain must contain the double or triple bond.
• Number the main chain so the double or triple bond gets the lowest possible number.
• Ethylene is a key raw material in polyethylene production.
• Ethylene is produced via cracking, breaking long hydrocarbon chains into smaller ones.
• Halogens can add to alkenes and alkynes with mild conditions.
• Hydrogen can be added across multiple bonds via hydrogenation, requiring high pressures and a catalyst.

Isomers

• Geometric isomers (cis-trans isomers) have the same bonding order but different atom arrangements in space.
• Double bonds in alkenes prevent free rotation, allowing geometric isomerism.
• Cis isomers have similar groups on the same side; trans isomers have them on opposite sides.
• Geometric isomers need a rigid structure preventing rotation and two different groups on each carbon.
• Cis-2-butene is polar, while trans-2-butene is nonpolar
• Heat or light can convert geometric isomers by breaking the pi bond and allowing rotation.
• Alkynes display structural isomerism but not geometric isomerism due to only one other group bonded to the carbon atoms in the triple bond.