Structure and Reactivity | Organic Chemistry 1

• A Bronsted acid is a proton donor and therefore contains a hydrogen atom. A proton loss from the acid forms its conjugate base
• A Bronsted base is a proton acceptor. It must be able to form a bond with a proton by donating an available electron pair. A proton gain by a base forms its conjugate acid 

Common examples of Bronsted acids are HCl, H₂SO₄, H₃O⁺, acetic acid (CH₃COOH), perchloric acid (HClO₄), p-toluenesulfonic acid (TsOH)

Common examples of Bronsted bases are HO^- (NaOH), RO^- (KO^tBu), H₂N^- (LiNH₂), R₂N^- (R₂NLi), H^- (KH)

A strong acid readily donates a proton, forming a weak conjugate base. The more easily an acid donates a proton, the smaller its pKa, the stronger it is. An acid can be deprotonated by the conjugate base of any acid with a higher pKa

The more stable a base is, the weaker the base and the stronger the conjugate acid

The effects that affect the stability of a base are:

• Resonance effects: the more forms a chemical compound has, the more stable it is
• Hybridization effect: lone pairs of electrons are stabilized by the s character of the orbital (25 % in sp³, 33 % in sp², and 50% in sp). Therefore, the increase in basicity correlates with hybridization as follows: sp < sp² < sp³
• Inductive effect: bases are stabilized by electron-withdrawing inductive effect (-I effect)

1. Draw the conjugate bases corresponding
2. Determine which conjugate base is more stable
3. Determine which acid is stronger: the more stable the conjugate base, the stronger the acid

• A Lewis acid is an electron pair acceptor. It must have an unfilled valence shell, a partial positive charge, or a proton
• A Lewis base is an electron pair donor and therefore contains a lone pair or a π bond. It donates this electron pair to any electron deficient compound

Common examples of Lewis acids are BF₃, AlCl₃, ⁺CR₃, H⁺

Common examples of Lewis bases are HO^-, RO^-, NH₃, NR₃, ^-NH₂, H₂O

A nucleophile is an electron-rich species that can form a covalent bond by donating a pair of electrons to an electron-poor atom, while an electrophile is an electron-poor species that can form a covalent bond by accepting a pair of electrons from a nucleophile

A nucleophile can be neutral or negatively charged and is usually symbolized by Nu^-. Lewis bases are nucleophiles, and lone pairs and π bonds are nucleophilic sites

An electrophile can be neutral or positively charged and is usually symbolized by E⁺. Lewis acids are electrophiles. Electronegative heteroatoms such as N, O, or halogens X create electrophilic carbon atoms

A functional group is an atom or a group of atoms with characteristic chemical and physical properties. It is the reactive part of the molecule

The most common functional groups in chemistry are: alkene, alkyne, arene, alkyl halide, ether alcohol, thiol, amine, and the carbonyl group (aldehyde, ketone, carboxylic acid, ester, amide)

The carbonyl group is composed of chemical species with a double bond C=O. The main families of the carbonyl group are aldehydes, ketones, carboxylic acids, esters, and amides

Isomers are molecules that have the same number and type of atoms but differ in the way their atoms are arranged. They have different chemical and physical properties

Constitutional isomers are chemical species that have the same molecular formula but differ in the way the atoms are bonded together, while stereoisomers are isomers that have the same molecular formula, the same bonds but differ in the way the atoms are oriented in space (different 3D geometry)

• A cis isomer is an isomer whose 2 substituents are on the same side of the ring or double bond
• A trans isomer is an isomer whose 2 substituents are located on either side of the ring or the double bond

Heterolytic cleavage is a bond break in which the electron pair of the bond is divided unequally between the products. A normal double-barbed arrow shows the movement of the pair of electrons. Heterolytic bond cleavage of a neutral molecule results in the formation of a cation and an anion

Homolytic cleavage is a bond break in which the electron pair of the bond is divided equally between the products. A single-barbed arrow shows the movement of a single electron. Homolytic cleavage of a bond results in the formation of radicals