Organic Molecules, Functional Groups, and Isomerism in GOB Chemistry

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 (General, Organic, and Biochemistry) 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 crucial in determining the properties and reactivity of organic compounds.

• 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 ($\ce{C=O}$).

Common Functional Groups in Organic Chemistry

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

• Aldehydes: Contain a carbonyl group ($\ce{C=O}$) bonded to at least one hydrogen atom.

• Ketones: Have a carbonyl group bonded to two carbon atoms.

• Carboxylic Acids: Feature a carbonyl group bonded to a hydroxyl group ($\ce{-COOH}$).

• Esters: Derived from carboxylic acids and alcohols, with the structure $\ce{R-COOR'}$.

• Amides: Contain a carbonyl group bonded to a nitrogen atom ($\ce{R-CONR_2}$).

Classification of Alcohols

Alcohols are classified based on the number of alkyl groups attached to the carbon bearing the hydroxyl group.

Type	Structure	Example
Primary (1°)	$\ce{R-CH2-OH}$	Ethanol
Secondary (2°)	$\ce{R_2CH-OH}$	Isopropanol
Tertiary (3°)	$\ce{R_3C-OH}$	Tert-butanol

Examples of Functional Groups

• Phenol: An aromatic ring with a hydroxyl group.

• Sorbitol: A sugar alcohol used as a low-calorie sweetener.

• Estradiol: A steroid hormone with phenol and alcohol functional groups.

Aldehydes and Ketones

Structure and Examples

Aldehydes and ketones are organic compounds containing the carbonyl functional group. Their chemical behavior is influenced by the groups attached to the carbonyl carbon.

• Aldehyde: $\ce{R-CHO}$ (e.g., benzaldehyde, almond flavoring)

• Ketone: $\ce{R-CO-R'}$ (e.g., acetoacetic acid, a by-product of fatty acid metabolism)

Carboxylic Acids and Amides

Carboxylic Acids

Carboxylic acids contain a carboxyl group ($\ce{-COOH}$) and are commonly found in biological molecules such as amino acids and fatty acids.

• Carboxylate: The deprotonated form of a carboxylic acid ($\ce{-COO^-}$).

• Example: Oleic acid (a monounsaturated fatty acid), amino acids (contain carboxylate group).

Esters and Amides

Esters and amides are derivatives of carboxylic acids, formed by condensation reactions with alcohols and amines, respectively.

Family Name	Representative Structure	Example Compound
Esters	$\ce{R-COOR'}$	Triglycerides (fats and oils)
Amides	$\ce{R-CONR_2}$	Peptide bonds in proteins

Isomerism

Types of Isomers

Isomerism refers to the phenomenon where molecules have the same molecular formula but different arrangements of atoms. This leads to different physical and chemical properties.

• 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

Chiral molecules have at least one carbon atom (chiral center) bonded to four different atoms or groups. Such molecules exist as two enantiomers, which are mirror images but not superimposable.

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

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

• Example: The two forms of lactic acid, D- and L-lactic acid.

Identifying Chiral Carbons

To identify chiral centers in a molecule, examine each tetrahedral carbon and determine if it is bonded to four different groups. An asterisk (*) is often used to mark chiral centers in structural formulas.

• Examine the entire group attached to the carbon, not just the atom directly bonded.

• Chiral centers are crucial in biochemistry, as many biological molecules are chiral.

Summary Table: Families of Organic Compounds and Functional Groups

Family Name	Functional Group Structure	Example Compound
Alcohol	$\ce{R-OH}$	Ethanol, Sorbitol
Aldehyde	$\ce{R-CHO}$	Benzaldehyde
Ketone	$\ce{R-CO-R'}$	Acetoacetic acid
Carboxylic Acid	$\ce{R-COOH}$	Oleic acid
Ester	$\ce{R-COOR'}$	Triglyceride
Amide	$\ce{R-CONR_2}$	Peptide bond

Additional info: These notes expand on the brief points in the original materials, providing definitions, examples, and structural formulas for key functional groups and isomer types relevant to GOB Chemistry.