Organic Chem Intro

Topic 4A: Introduction to Hazards and Risks

• Definition of Hazards and Risks
    - Hazard: Anything that could potentially cause harm.
    - Risk: The likelihood of that hazard actually causing harm.

• Context in Chemistry
    - Examples of hazards include:
      - Inhalation of harmful chemicals.
      - Spillage of harmful substances.
      - Contact with harmful chemicals or breaking glassware.

• Hazardous Properties Associated with Organic Compounds
    - Flammable: Easily ignites.
    - Volatile: Has a low boiling point, leading to rapid evaporation.
    - Toxic: Can cause damage to an organism.
    - Corrosive: Can damage living tissue.

• Risk Assessment
    - Importance of carrying out risk assessments when working with hazardous chemicals.
    - Involves identifying potential hazards in experiments and planning ways to reduce or eliminate risks.

• Reducing Risk
    - Methods to minimize risk during experiments:
      - Conducting experiments on a smaller scale.
      - Using less hazardous chemicals or equipment.

Hydrocarbons

• Definition
    - Organic chemistry primarily focuses on the properties and reactions of hydrocarbons, which are compounds containing only carbon and hydrogen atoms.

• Series of Compounds
    - Hydrocarbons belong to series with similar structures and formulas, represented in various forms.

Nomenclature

• Definition
    - Nomenclature refers to the set of rules governing the naming of organic compounds and their formula representations.

Formulas of Organic Compounds

• Types of Formulas
    1. Empirical Formula: The simplest whole number ratio of atoms of each element in a compound.
    2. Molecular Formula: Represents the actual number of atoms of each element in a compound.
    3. General Formula: All members of a homologous organic series adhere to a general formula.
    4. Structural Formula: Shows the arrangement of atoms within a molecule.
    5. Displayed Formula: Illustrates every atom and bond in an organic compound.
    6. Skeletal Formula: Displays only the bonds in a compound and any non-carbon atoms; vertices represent carbon atoms, and hydrogen is implied unless otherwise stated.

Homologous Series

• Definition
    - Organic compounds are typically part of a homologous series characterized by a general formula, with each consecutive member differing by $CH_2$.
    - Increase in boiling points correlates with chain length.
    - Each series has a functional group that determines its chemical reactivity.

Naming Compounds

• IUPAC Naming Rules
    - Compounds are named per International Union of Pure and Applied Chemistry (IUPAC) guidelines to avoid confusion.
    - Understanding both how to name based on structure and how to draw structures from names is essential.
    - Stem: Prefix indicates the length of the longest unbroken carbon chain (first 10 using alkanes as an example).

• Functional Groups
    - The suffix indicates the functional group present. If multiple functional groups exist, they are prefixes.

Prefixes for Functional Groups

• Halogens
    | Functional Group | Prefix |
    |---------------- |--------- |
    | Fluorine | Fluoro- |
    | Chlorine | Chloro- |
    | Bromine | Bromo- |
    | Iodine | Iodo- |

• Side Chains
    - Side chains are represented as prefixes using alkyl group stems with -yl suffix.

General Naming Rules

  - Apply the following guidelines when naming:
    1. Functional groups and side chains are assigned numbers according to their attachment to carbon atoms.
    2. Numbers are separated by commas.
    3. Numbers and words are separated by hyphens.
    4. For multiple groups, use di- (2), tri- (3), tetra- (4), etc.
    5. Chain numbering begins from the end closest to functional groups.
    6. Use alphabetical order for multiple prefixes.

• Examples:
    - Butan-2,3-diol: A compound with two alcohol functional groups located at carbons 2 and 3.
    - 3-ethyl,5-methylhexan-2-ol: Another compound example.
    - Propanone (or Propan-2-one): Acetone, where the ketone can only exist at position 2; thus, the number is unnecessary.
    - 1,2-dichloropropane: Example of a compound with multiple functional groups.

Reaction Mechanisms

• Types of Reactions
    - Reactions can be categorized by changes in reactants and products:
      - Addition Reaction: Reactants combine to form one product.
      - Substitution Reaction: One functional group is replaced by another.
      - Oxidation Reaction: A species loses at least one electron (oxidation).
      - Reduction Reaction: A species gains at least one electron (reduction).
      - Polymerization Reaction: Small molecules (monomers) link to form a polymer.

• Free Radicals and Electrophiles
    - Free Radicals: Highly reactive species with unpaired electrons.
    - Electrophiles: Electron acceptors attracted to high electron density areas.

Mechanisms

• Mechanisms illustrate electron movement with curly arrows.

Bond Breaking Types

• Covalent Bond Breaking Types:
    - Homolytic Fission: Electrons divide evenly between atoms, each forming a free radical.
    - Heterolytic Fission: One atom receives both electrons, creating ions:
      - Negative ion forms on the gaining atom; a positive ion forms on the other.

Topic 4B: Alkanes

• Definition
    - Alkanes are saturated hydrocarbons with all single carbon-carbon bonds, belonging to the homologous series with general formula $C_nH_{2n+2}$.
    - Cycloalkanes also qualify as saturated hydrocarbons but are exceptions to this general formula.

Isomerism

• Definition
    - Isomers are molecules with the same molecular formula but differing arrangements of atoms.

Structural Isomers

• Definition
    - Have the same molecular formula but different structural arrangements.
    - Can appear as straight or branched chains.

Position Isomers

• Definition
    - Position isomers feature different functional group locations on the carbon chain.

Functional Group Isomers

• Definition
    - Feature different arrangements resulting in varied functional groups.

Fractional Distillation

• Process
    - Crude oil is a complex mixture of hydrocarbons that can be separated via fractional distillation based on boiling points:
      1. Vapourize the mixture and feed it into a fractionating column.
      2. Vapors rise, cool, and condense at different levels.
      3. Collect products at various heights based on carbon chain lengths.

Cracking

• Definition
    - Cracking breaks long carbon chains into shorter, more useful molecules under harsh conditions, through two main processes:

Thermal Cracking

• Produces alkanes and alkenes under high temperatures ($1200 K$) and large pressures ($7000 kPa$).

• Always results in an alkane with remaining atoms forming an alkene having the general formula $C_nH_{2n}$.

Catalytic Cracking

• Produces aromatic compounds utilizing lower temperatures ($720 K$) and normal pressures alongside zeolite catalysts.

Combustion of Alkanes

• Definition
    - Alkanes serve as quality fuels due to the energy release during combustion.
    - Complete combustion: sufficient oxygen yields $CO_2$ and water.
    - Incomplete combustion: when oxygen is restricted, produce $CO$ or carbon alongside water, which can be hazardous due to physiological impacts (binding with hemoglobin in the blood and causing suffocation).

• Byproducts
    - Oxides of nitrogen and sulfur also result from combustion, contributing to acid rain and environmental degradation.
    - Carbon particulates emitted may lead to respiratory issues and global dimming.

• Catalytic Converters
    - Utilize a rhodium catalyst to convert harmful unburnt hydrocarbons and nitrogen oxides into stable byproducts ($CO_2$ and $H_2O$).

Alternative Fuels

• Definition
    - Development of alternative fuels, including biofuels that combust with fewer harmful emissions.

• Ethanol
    - Considered carbon-neutral as combustion emissions equal carbon absorption during crops' growth.
    - Produced through fermentation from starch-broken sugars, rendering it slow with low yield but ecologically favorable.

• Hydrogen
    - Also carbon-neutral, with water as the only combustion byproduct.

Chlorination of Alkanes

• Mechanism Overview
    - Alkanes react with halogens in UV light presence, generating halogenoalkanes:

Steps of Reaction

1. Initiation
      - UV radiation breaks halogen bonds (homolytic fission), forming free radicals.

2. Propagation
      - A hydrogen atom is replaced by a halogen, reforming the halogen radical.

3. Termination
      - Two radicals combine, ceasing reaction.

• The propagation phase can lead to multiple substitutions, resulting in a chain reaction that can introduce various products, complicating organic synthetic uses.

• Mechanism Representation
    - The mechanism is illustrated using half-arrows for single electron movements.