Unit_2_Review__Organic

Unit 2 Review Organic Chemistry

Introduction to Organic Chemistry

• Organic compounds are primarily composed of carbon atoms that are bonded to hydrogen atoms and a few other elements.

• Examples of organic substances include wood and plastics.

• In contrast, inorganic substances lack carbon or do not possess carbon-carbon or carbon-hydrogen bonds (e.g., calcium carbonate (CaCO3), carbon dioxide (CO2)).

Properties of Organic Compounds

Properties of Carbon Atoms

1. Four Bonding Electrons

   • Each carbon atom can form four covalent bonds.

   • Carbon can also bond with elements like hydrogen, oxygen, nitrogen, phosphorus, sulfur, and the halogens.

2. Types of Bonds

   • Carbon can form strong single, double, and triple bonds with other carbon atoms.

   • Carbon atoms can create long chains, making organic compounds relatively stable.

3. Diverse Structures

   • Carbon can bond in various formations including straight chains, branched chains, sheets, tubes, and spheres.

General Properties of Organic Compounds

• Most organic compounds are molecular and consist of covalent bonds.

• Carbon's four valence electrons can create multiple bond configurations:

  • Four single bonds.

  • A combination of double and single bonds.

  • Triple bond alongside single bonds.

Representing Bonds

Types of Bonds and Their Representation

• Single Bond: A bond formed by sharing a pair of electrons; represented as a solid line.

• Double Bond: Formed by sharing two pairs of electrons; represented by two solid lines.

• Triple Bond: Involves sharing three pairs of electrons; represented by three solid parallel lines.

Hydrocarbons

Definition and Types

• Hydrocarbons consist solely of carbon (C) and hydrogen (H) atoms.

• Major types of hydrocarbons include:

  • Alkanes: Saturated hydrocarbons containing only single bonds (General formula: CnH2n+2).

  • Alkenes: Unsaturated hydrocarbons with at least one carbon-carbon double bond.

  • Alkynes: Unsaturated hydrocarbons with at least one carbon-carbon triple bond.

Alkanes

• Simplest form of hydrocarbons featuring only single covalent bonds (e.g., methane, ethane).

• Straight-chain alkanes grow by each addition of a -CH2 group, forming a continuous chain.

Structural Representation of Organic Molecules

Types of Structural Formula

1. Structural Formula: Indicates all atoms and bonds explicitly, using straight lines. However, requires more space.

2. Condensed Structural Formula: More compact, omitting certain bonds but preserving side branches (e.g., CH3-CH2-CH2-CH3).

3. Line Structural Formula: Depicts bonds through lines, where each line end represents carbon atoms.

4. Ball-and-Stick Model: Shows relative atom sizes and angles in three dimensions.

5. Space-filling Model: Highlights the size of atoms and overall molecular space, with bonds not depicted.

Branching in Alkanes

• Branched-chain alkanes have carbon atoms connected to more than two other carbons.

• Recognition of branched alkanes includes the use of functional groups (side groups).

Isomerism in Alkanes

Structural Isomers

• Isomers possess the same chemical formula but differ in structure, which leads to different properties.

• Branching introduces multiple isomeric forms.

Naming Alkanes

Basic Nomenclature Rules

• Names consist of a root indicating the number of carbons in the longest chain and a suffix (-ane for alkanes).

• Examples include:

  • Methane (1 carbon)

  • Ethane (2 carbons)

• When naming branched alkanes, prefixes indicate the positions and names of branches.

Unsaturated Hydrocarbons

Properties of Alkenes and Alkynes

• Alkenes (double bond) and alkynes (triple bond) exhibit higher reactivity due to the instability of their multiple bonds.

• Both types of hydrocarbons follow specific naming conventions based on their functional group.

  • Alkenes: CnH2n (e.g., ethene)

  • Alkynes: CnH2n-2 (e.g., ethyne)

Functional Groups in Organic Chemistry

• Functional groups define the chemical behavior of organic compounds:

  • E.g., alcohols contain -OH, carboxylic acids contain -COOH, etc.

• Functional groups modify the properties of parent hydrocarbons significantly.

Combustion Reactions

Types of Combustion

1. Complete Combustion: Occurs in sufficient oxygen, producing CO2 and H2O.

   • Example reaction: CxHy + O2 → CO2 + H2O

2. Incomplete Combustion: Occurs in limited oxygen, producing carbon monoxide, soot, and H2O.

Balancing Combustion Reactions

• Steps:

  • Balance carbon, hydrogen, and oxygen in the equation systematically.

  • If fractions arise, multiply through to achieve whole numbers.

Reactions of Alkenes and Alkynes

Addition Reactions

• Both undergo addition reactions due to their unsaturated nature, allowing for the addition of multiple atoms.

• Example: Hydrogenation converts ethene to ethane.

Elimination Reactions

• These reactions involve the removal of atoms to create double bonds from single bonds.

• Types include dehydration and elimination of HX (where X is a halogen).

Stereoisomerism

Types

• Positional isomers alter the location of functional groups in a molecule without changing the formula.

• Stereoisomers differ in spatial orientation:

  • Cis-Trans Isomerism: Variation in the arrangement of groups relative to double bonds.