Lecture #2: Organic Chemistry Basics

Ionic bond

A bond formed between a metal and a nonmetal due to the transfer of electrons.

Covalent bond

A bond formed between two nonmetals due to the sharing of electrons.

Empirical formula

Gives the relative number of atoms of each element in a compound, representing the simplest whole-number ratio of atoms.

Molecular formula

Gives the actual number of atoms of each element in a molecule.

Structural formula

Shows how atoms are connected to each other; shows covalent bonds explicitly using lines to represent bonds.

Skeletal structures

Organic structures that omit hydrogen atoms for clarity except on heteroatoms, where vertices and line ends represent carbon atoms.

Hydrocarbon

Organic compounds containing only carbon and hydrogen.

Primary (1°) carbon

An alkane carbon bonded to one other carbon.

Secondary (2°) carbon

An alkane carbon bonded to two other carbons.

Tertiary (3°) carbon

An alkane carbon bonded to three other carbons.

Quaternary (4°) carbon

An alkane carbon bonded to four other carbons.

Functional groups

Key “corner pieces” in understanding how organic molecules behave in reactions, enabling prediction of reactivity, acids/bases, and physical properties.

sp^3 hybridization

Occurs when an atom has 4 electron groups, forms 4 \\sigma -bonds, and has a tetrahedral geometry (e.g., methane).

sp^2 hybridization

Occurs when an atom has 3 \\sigma -bonds and 1 \\pi -bond, resulting in planar geometry and trigonal planar arrangement around the carbon (e.g., ethene).

sp hybridization

Occurs when an atom has 2 \\sigma -bonds and 2 \\pi -bonds, resulting in linear geometry and enabling a triple bond (e.g., acetylene).

Ionic bond

A bond formed between a metal and a nonmetal due to the transfer of electrons.

Covalent bond

A bond formed between two nonmetals due to the sharing of electrons.

Empirical formula

Gives the relative number of atoms of each element in a compound, representing the simplest whole-number ratio of atoms. Example: CH_2O for glucose.

Molecular formula

Gives the actual number of atoms of each element in a molecule. Example: C_6H_{12}O_6 for glucose.

Structural formula

Shows how atoms are connected to each other, explicitly using lines to represent covalent bonds.

Skeletal structure

A representation of organic molecules that omits hydrogen atoms (except on heteroatoms) and shows carbon atoms at vertices and line ends, with lines representing bonds.

Organic compound

A class of molecular compounds that contain at least one carbon–hydrogen (C–H) bond.

Heteroatom

Any atom other than carbon or hydrogen in an organic compound.

Hydrocarbon

Organic compounds containing only carbon and hydrogen.

Alkane

A saturated hydrocarbon containing only single carbon-carbon bonds.

Alkene

An unsaturated hydrocarbon containing at least one carbon-carbon double bond (C=C).

Alkyne

An unsaturated hydrocarbon containing at least one carbon-carbon triple bond (C\equiv C).

Primary (1°) carbon

An alkane carbon atom bonded to one other carbon atom.

Secondary (2°) carbon

An alkane carbon atom bonded to two other carbon atoms.

Tertiary (3°) carbon

An alkane carbon atom bonded to three other carbon atoms.

Quaternary (4°) carbon

An alkane carbon atom bonded to four other carbon atoms.

Functional group

Specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules, allowing prediction of reactivity and physical properties.

Carboxylic acid

An organic functional group with the general formula R-COOH, typically named with the suffix -oic -acid.

Ester

An organic functional group with the general formula R-COO-R', typically named with the suffix -oate.

Ether

An organic functional group with the general formula R-O-R', often named as an alkyl alkyl ether.

Aldehyde

An organic functional group with the general formula R-CHO, typically named with the suffix -al.

Ketone

An organic functional group with the general formula R-CO-R', typically named with the suffix -one.

Alcohol

An organic functional group with the general formula R-OH, typically named with the suffix -ol.

Amine

An organic functional group containing a nitrogen atom bonded to one or more carbon atoms, with general formulas like R-NH_2 (primary), typically named with the suffix -amine.

Halide

An organic functional group with the general formula R-X, where X is a halogen (F, Cl, Br, I).

sp^3 hybridization

Occurs when an atom has 4 electron groups (4 \sigma -bonds), resulting in a tetrahedral geometry with bond angles of 109.5^{\circ}. Example: carbon in methane (CH_4).

sp^2 hybridization

Occurs when an atom has 3 electron groups (3 \sigma -bonds and 1 \pi -bond), resulting in a trigonal planar geometry with bond angles of 120^{\circ}. Example: carbon in ethene (C_2H_4).

sp hybridization

Occurs when an atom has 2 electron groups (2 \sigma -bonds and 2 \pi -bonds), resulting in a linear geometry with bond angles of 180^{\circ}. Example: carbon in acetylene (C_2H_2).

R-group

A generic symbol used in organic chemistry to denote 'the rest of the molecule' not currently being analyzed or discussed, simplifying complex structures.

Aromatic hydrocarbon