Organic Molecules, Functional Groups, and Isomerism: GOB Chemistry Study Notes

Organic Molecules

Introduction to Organic Molecules

Organic molecules are compounds primarily composed of carbon and hydrogen, often containing other elements such as oxygen, nitrogen, and sulfur. These molecules form the basis of life and are central to biochemistry and GOB Chemistry.

• Organic compounds are defined by the presence of carbon atoms bonded to hydrogen and other elements.

• Other atoms present in organic compounds, aside from carbon and hydrogen, are called heteroatoms.

Functional Groups

Definition and Importance

Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. They are key to understanding organic chemistry and biochemistry.

• A functional group is a group of atoms bonded in a particular way that imparts specific chemical properties to a molecule.

• Common heteroatoms in functional groups include oxygen, nitrogen, and sulfur.

• Functional groups containing a carbon double-bonded to oxygen are called carbonyl groups.

Common Functional Groups in Organic Chemistry

• Alcohols: Characterized by the presence of a hydroxyl group (-OH) attached to a carbon atom.

• Aldehydes: Contain a carbonyl group (C=O) with the carbon atom also bonded to a hydrogen atom.

• Ketones: Have a carbonyl group (C=O) bonded to two carbon atoms.

• Carboxylic Acids: Feature a carbonyl group bonded to a hydroxyl group (-COOH).

• Esters: Derived from carboxylic acids and alcohols, with the general structure R-COOR'.

• Amides: Contain a carbonyl group bonded to a nitrogen atom.

Representative Structures and Examples

Family Name	Representative Structure	Example Compound
Alcohol	Primary: R-CH2-OH Secondary: R2CH-OH Tertiary: R3C-OH	Sorbitol (sweetener), Phenol, Estradiol
Aldehyde	R-CHO	Benzaldehyde (almond flavor)
Ketone	R-CO-R'	Acetoacetic acid (fatty acid metabolism)
Carboxylic Acid	R-COOH	Oleic acid (fatty acid), Amino acids (carboxylate form)
Ester	R-COOR'	Triglycerides (fats and oils)
Amide	R-CONH2	Peptide bonds in proteins

Isomerism

Types of Isomers

Isomerism refers to the phenomenon where two or more molecules have the same molecular formula but different arrangements of atoms. Isomers can be classified as structural or stereoisomers.

• Structural isomers: Molecules with the same molecular formula but different connectivity of atoms.

• Conformational isomers (conformers): Molecules with the same connectivity but different spatial orientation due to rotation around single bonds.

• Stereoisomers: Molecules with the same connectivity but different spatial arrangement of atoms.

• Enantiomers: Stereoisomers that are nonsuperimposable mirror images of each other.

Chirality and Enantiomers

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Chiral molecules contain at least one chiral center, typically a carbon atom bonded to four different groups.

• Chiral center: A tetrahedral carbon atom bonded to four different atoms or groups.

• Enantiomers have identical physical properties except for their interaction with plane-polarized light and reactions in chiral environments.

• To identify chiral centers, examine each tetrahedral carbon and check if all four attached groups are different.

• An asterisk (*) is often used to mark chiral centers in structural formulas.

Examples and Applications

• Enantiomers are important in pharmaceuticals, as different enantiomers of a drug can have different biological effects.

• Chiral molecules are common in biomolecules such as amino acids and sugars.

Summary Table: Types of Isomerism

Type	Description	Example
Structural Isomer	Different connectivity of atoms	Butane vs. isobutane
Conformational Isomer	Same connectivity, different rotation	Staggered vs. eclipsed ethane
Stereoisomer	Same connectivity, different spatial arrangement	Cis/trans alkenes
Enantiomer	Nonsuperimposable mirror images	L- and D-glucose

Key Equations

• General formula for number of stereoisomers:

$2^n$

where n is the number of chiral centers in the molecule.

Additional info:

• Functional groups determine the reactivity and properties of organic molecules, which is essential for understanding biochemical processes.

• Chirality is crucial in biochemistry, as many biological molecules are chiral and only one enantiomer is biologically active.