Introduction to organic chemistry Flashcards
Nomenclature, reaction mechanisms, isomerism (17 cards)
What are the different ways to represent organic compounds?
Empirical formula – simplest whole number ratio of atoms (e.g., CH₂O)
Molecular formula – actual number of atoms (e.g., C₂H₄O₂)
General formula – algebraic formula for a homologous series (e.g., CₙH₂ₙ₊₂ for alkanes)
Structural formula – shows arrangement of atoms carbon by carbon (e.g., CH₃CH₂OH)
Displayed formula – shows all bonds and atoms
Skeletal formula – shows bonds between carbons as lines; hydrogen and carbon atoms not drawn
What is a homologous series?
A series of organic compounds with:
The same functional group
The same general formula
Similar chemical properties
Gradual change in physical properties
Each member differing by a CH₂ group
✅ Example: alkanes (methane, ethane, propane…)
What is the IUPAC system for naming organic compounds?
Longest carbon chain is the root name (meth-, eth-, prop-, etc.)
Suffix shows main functional group (-ol, -al, -one, etc.)
Prefixes for side chains or other functional groups (e.g., methyl-, chloro-)
Numbering the chain to give the lowest number to functional group or branch
✅ Double/triple bonds = -ene/-yne with position number
What do students need to be able to draw from the IUPAC name?
Structural formulas (e.g., butan-2-ol → CH₃CH(OH)CH₂CH₃)
Displayed formulas (showing all bonds explicitly)
Skeletal formulas (zig-zag lines, carbon at ends and bends)
✅ Limited to up to 6 carbon atoms in chains and rings
What is a reaction mechanism in organic chemistry?
A reaction mechanism is a step-by-step sequence that shows how a reaction takes place at the particle level.
✅ It includes the movement of electrons and the formation/breaking of bonds.
What is a free radical and how is it represented?
A free radical is a species with an unpaired electron, represented by a single dot (*).
✅ They are highly reactive.
❌ Curly arrows are not used in radical mechanisms.
What are the three main steps in a free radical mechanism?
Initiation – radicals are formed (e.g., by UV light)
Propagation – radicals react to make more radicals
Termination – two radicals combine to form a stable molecule
✅ Example: chlorination of methane
How do you write equations for a free radical mechanism?
Use balanced equations for each step:
Initiation: Cl₂ → 2Cl*
Propagation: Cl* + CH₄ → HCl + CH₃*
CH₃* + Cl₂ → CH₃Cl + Cl*
Termination: Cl* + Cl* → Cl₂
✅ Use dots to show radicals
What does a curly arrow represent in organic mechanisms?
A curly arrow (↷) shows the movement of an electron pair.
Starts from a lone pair or a bond
Points to where a new bond is formed or where a bond is broken
What are students expected to show when drawing mechanisms with curly arrows?
Structures of all species involved
Use curly arrows to show:
Bond formation (starts from a lone pair or bond)
Bond breaking (arrow from bond to atom)
✅ Common in nucleophilic substitution, electrophilic addition, etc.
Define structural isomerism.
Structural isomers have the same molecular formula but different structural formulas — atoms are connected in different ways.
What are the three types of structural isomers?
Chain isomers – different arrangements of the carbon chain (e.g., straight vs branched).
Position isomers – functional group in different positions on the same carbon chain.
Functional group isomers – same atoms arranged into different functional groups.
Define stereoisomerism.
Stereoisomers have the same structural formula but different spatial arrangements of atoms.
What causes E–Z isomerism?
E–Z isomerism arises due to restricted rotation around the C=C double bond in alkenes.
How do you distinguish between E and Z isomers?
Use the Cahn–Ingold–Prelog (CIP) priority rules:
Look at the atomic numbers of atoms bonded to each C of the double bond.
Z (zusammen) = higher priority groups on the same side.
E (entgegen) = higher priority groups on opposite sides.
How do CIP rules assign priority in E–Z isomers?
Compare the atomic number of the first atom attached to each carbon of the C=C bond.
The atom with the higher atomic number gets higher priority.
If atoms are the same, look at the next bonded atoms (until a difference is found).
What should students be able to do related to isomerism?
Draw chain, position, and functional group isomers.
Draw E and Z isomers using structural formulas.
Apply CIP priority rules to identify and name E/Z isomers.
