Basic Medical Chemistry Study Guide

Course Information

• Department: Pharmaceutical Chemistry

• Program: Faculty of Pharmacy and Pharmaceutical Sciences, College of Health Science

• Course Code: SMS 151

• Course Title: Basic Medical Chemistry

• Year: 2025

• Instructor: Prof. Isaac Ayensu

Learning Outcomes

• At the end of the module, students should be able to:

  • Classify organic compounds into homologous series.

  • Predict their chemical and physical properties.

  • Appreciate and discuss their use in medicine.

  • Provide examples of medicinal, household, or industrial chemicals that belong to various functional groups.

Overview of Content

1. Introduction to Organic Chemistry

2. Hydrocarbons

   • Classification

   • Alkane Family

   • Isomerism

   • Nomenclature

   • Physical and Chemical Properties

   • Hydrocarbon Sources

   • Reactions of Alkanes

3. Hydrocarbon Derivatives

4. Chemistry Connections

Introduction to Organic Chemistry

• Definition: Organic chemistry is the study of carbon and its compounds.

• Sources of Carbon: Major sources include fossil fuels:

  • Petroleum

  • Natural gas

  • Coal

• Approximately 7 million organic compounds account for 90% of all known substances.

• Each year, over 50,000 new organic compounds are synthesized.

Hydrocarbons

• Definition: A hydrocarbon is a compound that contains only carbon and hydrogen.

• Hydrocarbon Derivative: A compound derived from a hydrocarbon with other elements (e.g., fluorine, nitrogen, oxygen).

• Types of Hydrocarbons:

  • Saturated Hydrocarbons: Have only single bonds between carbon atoms.

  • Family: Alkanes

  • Unsaturated Hydrocarbons: Contain double or triple bonds.

  • Types:

    • Alkenes: Hydrocarbons with double bonds.

    • Alkynes: Hydrocarbons with triple bonds.

    • Aromatic Hydrocarbons: Contain a benzene ring; a 6-membered ring of carbon atoms with alternating single and double bonds.

Classification of Hydrocarbons

• Hydrocarbons can be classified into:

  • Aliphatic Hydrocarbons with C—C and C—H $ ext{σ}$ bonds.

  • Acyclic Alkanes: Follow the molecular formula $C_nH_{2n+2}$; contain only linear and branched chains of carbon atoms.

    • Maximum hydrogen atoms per carbon.

  • Cycloalkanes: Carbons joined in rings.

  • Molecular formula $C_nH_{2n}$; have two fewer H atoms than an acyclic alkane with the same number of carbons.

Alkanes

• Definition: Alkanes are saturated hydrocarbons (or aliphatic hydrocarbons).

• General Formula: $C_nH_{2n+2}$.

• Examples:

  • Methane (CH4)

  • Ethane (C2H6)

  • Propane (C3H8)

  • Butane (C4H10)

Lewis Structures of Alkanes

• Methane:

  • Expanded:

  • H–C–H

  • H--C--H

  • Condensed: $CH_4$

• Ethane:

  • Expanded:

  • H–C–C–H

  • Condensed: $CH_3-CH_3$

• Propane:

  • Expanded:

  • H–C–C–C–H

  • Condensed: $CH_3-CH_2-CH_3$

• Butane:

  • Expanded:

  • H–C–C–C–C–H

  • Condensed: $CH_3-CH_2-CH_2-CH_3$

Structure Characteristics of Alkanes

• All carbon atoms in alkanes are surrounded by four groups; they are sp3 hybridized, with a tetrahedral geometry (all bond angles are $109.5^ ext{o}$).

• Applications:

  • Lighter alkanes (1–10 carbons) are used as fuels.

  • Larger alkanes (20–40 carbons) are solids used to make waxes and candles.

Classification of Carbons in Alkanes

1. Primary Carbon ($1^ ext{o}$): Connected to one carbon atom.

2. Secondary Carbon ($2^ ext{o}$): Connected to two carbon atoms.

3. Tertiary Carbon ($3^ ext{o}$): Connected to three carbon atoms.

Isomerism in Alkanes

• Definition: Isomerism occurs when two different structures have the same molecular formula but different carbon configurations.

• Examples using butane (C4H10):

  • Structure 1: Normal butane

  • Structure 2: Isobutane (branched)

• Questions posed about isomers for alkanes, for instance, how many isomers exist for C5H12?

• Answer: There are three isomers of C5H12.

Nomenclature of Alkanes

1. Common System:

   • Best for low molecular weight hydrocarbons.

   • Steps for naming:

   1. Count total carbon atoms.

   2. Use the Latin root corresponding to carbon count followed by the suffix “-ane”.

   3. For unbranched alkanes, use prefix "normal" or "n-"; specific prefixes for branched hydrocarbons.

2. Systematic Nomenclature (IUPAC):

   • Find the longest continuous chain of carbon atoms.

   • Name substituents using locator numbers and alphabetical order.

   • Use di-, tri-, etc., for multiple substituents.

Examples of Nomenclature

• Common names for the alkanes:

  • 1 Carbon: Meth-

  • 2 Carbons: Eth-

  • 3 Carbons: Prop-

  • 4 Carbons: But-

• Systematic Example: For a compound with 4 carbons and substitution, the name might be 3-ethyl-2,6-dimethylheptane, ensuring proper alphabetical placement and lowest chain numbering.

Properties of Alkanes

• Physical Properties:

  • Alkanes have no color or odor.

  • Lower density (< 1 g/mL), float on water.

  • Poor solubility in polar solvents; dissolve readily in non-polar solvents (hydrophobic).

  • Relatively low melting and boiling temperatures; generally increase with carbon chain length.

• Chemical Properties:

  • Unreactive compared to organic compounds with functional groups.

  • Undergo halogenation reactions and combustion reactions.

Reactions of Alkanes

1. Halogenation: Reactions involving alkanes and halogens, typically via free-radical mechanisms.

2. Combustion: Reacts with oxygen to produce carbon dioxide and water, often releasing energy (heat).

   • Example reactions include combustion of propane: $C_3H_8 + 5O_2 → 3CO_2 + 4H_2O + ext{heat}$.

Hydrocarbon Derivatives

• Definition: Hydrocarbon derivatives feature a functional group beyond just C–H bonds, categorizing into two groups based on the presence or absence of a carbonyl group (C=O).

• Classes of Compounds:

  • Non-Carbonyl Derivatives: I.e., alcohols, ethers, etc.

  • Carbonyl Derivatives: I.e., aldehydes, ketones, etc.

• Examples:

  • Organic halides are formed when a halogen replaces a hydrogen in a hydrocarbon: used as solvents.

  • Alcohols contain a hydroxyl group and exhibit higher water solubility compared to their parent alkanes due to hydrogen bonding.

Applications of Alkanes in Medicine

1. Anesthetics: Certain haloalkanes (e.g., halothane) used for anesthesia.

2. Pharmaceuticals: Alkanes act as solvents in drug formulations, especially for hydrophobic drugs.

3. Paraffin: Used in medical treatments, such as paraffin baths.

4. Lubricants/Emollients: Alkanes aid in topical medications and lubricants in devices.

• Examples of Medications:

  • Benzonatate (non-narcotic cough suppressant)

  • Perindopril (ACE inhibitor for hypertension)

  • Busulfan (alkylating agent for leukemia treatment)

  • Propofol (sedative for general anesthesia)

  • Lacosamide (anti-epileptic medication).

Environmental Impact of Alkanes

• Major energy sources with methane, propane, butane as fuel components.

• Pollution through carbon dioxide emissions increasing climate change risks; carbon monoxide can be a hazardous byproduct of incomplete combustion.

• Crude Oil: Alkanes are primary constituents, with refining producing various products for chemicals and fuels.

Summary of Hydrocarbons

• Organic chemistry covers all carbon-containing compounds, specifically hydrocarbons (C/H).

• Hydrocarbons are categorized into saturated (single bonds) and unsaturated (double/triple bonds).

• Hydrocarbon derivatives possess functional groups impacting their chemistry and usage in various applications, including medicine and industry.

Important Note

• This document serves as a comprehensive study guide encapsulating the key topics, definitions, classifications, properties, methodologies, and applications in Basic Medical Chemistry as taught in this course at KNUST.

Acknowledgement

• This course is backed by the commitment to provide quality education and research at KNUST as indicated by global rankings.