4a-Introduction Flashcards
Q: What is a hydrocarbon?
A hydrocarbon is a compound that contains only hydrogen and carbon atoms. Examples include methane (CH₄), ethane (C₂H₆), and propane (C₃H₈).
Q: What are the different ways to represent organic molecules?
Organic molecules can be represented in several ways:
Empirical formula:
Molecular formula:
General formula:
Structural formula:
Displayed formula:
Empirical formula:
Shows the simplest ratio of atoms (e.g., CH₂ for ethene).
Molecular formula:
Shows the actual number of atoms (e.g., C₂H₄ for ethene).
General formula:
Represents an entire homologous series (e.g., alkanes: CₙH₂ₙ₊₂, alkenes: CₙH₂ₙ).
Structural formula:
Shows how atoms are arranged in a molecule (e.g., CH₃CH₃ for ethane).
Displayed formula:
Shows all atoms and bonds explicitly (e.g., ethene: H₂C=CH₂).
Q: What is a homologous series?
A homologous series is a family of organic compounds that:
Have the same general formula
Differ by a CH₂ unit between consecutive members
Show similar chemical properties
Have a gradual change in physical properties (e.g., boiling points increase with molecular size)
Q: What is a functional group?
A functional group is a specific group of atoms in a molecule responsible for its chemical reactions. Examples include:
Alkenes (-C=C-)
Alcohols (-OH)
Carboxylic acids (-COOH)
Q: What is isomerism?
Isomerism occurs when compounds have the same molecular formula but different structural arrangements.
Types of isomers : Structural isomerism
Structural isomerism: Different connectivity of atoms (e.g., butane vs. methylpropane)
Geometric (cis-trans) isomerism: Occurs in alkenes due to restricted rotation around the double bond
Types of isomers :
Geometric (cis-trans) isomerism:
Occurs in alkenes due to restricted rotation around the double bond
Q: How do you name organic compounds following IUPAC rules?
The IUPAC system follows these rules:
Identify the longest carbon chain (base name: methane, ethane, propane, etc.)
Identify and number the functional group (e.g., alcohol -OH at carbon 2 → propan-2-ol)
Identify and number any substituents (e.g., methyl, ethyl, chloro, etc.)
Arrange substituents alphabetically with the correct position numbers
Examples:
C₄H₁₀ (butane)
CH₃CH(CH₃)CH₃ (2-methylpropane)
CH₃CH=CH₂ (propene)
CH₃CH₂OH (ethanol)
Q: How do you write structural and displayed formulae?
A: Given a molecular formula, use these steps:
Identify the main chain and its functional group.
Draw the correct number of carbon and hydrogen atoms.
Include any functional groups or branching correctly.
Example:
Molecular formula: C₃H₆O
Possible structural formulae:
Propanal (CH₃CH₂CHO)
Propanone (CH₃COCH₃)
Displayed formula: Shows all bonds explicitly
How are organic reactions classified?A: Organic reactions three main types:
Substitution Reactions:
Substitution Reactions:
One atom or group is replaced by another.
Example: CH₄ + Cl₂ → CH₃Cl + HCl (Methane reacts with chlorine under UV light.)
How are organic reactions classified?A: Organic reactions three main types:
Addition Reactions:
Addition Reactions:
A reactant is added to a molecule without removing any atoms.
Example: C₂H₄ + Br₂ → C₂H₄Br₂ (Ethene reacts with bromine, confirming the presence of a double bond.)
How are organic reactions classified?A: Organic reactions three main types:
Combustion Reactions:
Hydrocarbons react with oxygen to produce CO₂ and H₂O (complete combustion) or CO and H₂O (incomplete combustion).
Example:
Complete combustion: CH₄ + 2O₂ → CO₂ + 2H₂O
Incomplete combustion: CH₄ + O₂ → CO + 2H₂O
