Jason Cameron

Organic Chemistry

9 min read

Intramolecular forces

You can’t break covalent bonds without a chemical change.

Intermolecular forces

Forces of attraction between two molecules

Much weaker than intramolecular forces

  • Dictate physical changes
  • Does not change the substance
LDF (London Dispersion Forces)
  • Temporary force based on which side of the atom the electrons are on
  • The strength is directly related to the number of electrons and protons in the given molecule
  • Present in ALL molecules
  • Stronger in larger, more polarizable molecules
Dipole-Dipole
  • Occurs between polar molecules having dipoles
  • Polarity is determined by the polarity of the bond and the shape of the molecule
  • Stronger than LDF but weaker than hydrogen bonds
H-Bonds (Hydrogen Bonds)
  • Type of dipole-dipole interaction
  • Strongest intermolecular force
  • Occurs between Hydrogen atoms in one molecule and highly electronegative atoms (F, O, N) in another
  • Still only 1/10 the strength of a covalent bond
  • Can ONLY happen with H bonded to F, O, or N

Isomers

Isomers are molecules that have the same molecular formula but differ in the arrangement of their atoms.

Structural (Constitutional) Isomers
  • Atoms are connected in a different order (different bonding sequence)
  • They have different IUPAC names and often different physical and chemical properties
  • Functional Group Isomers: A subtype of structural isomers where the molecules have the same molecular formula but different functional groups (e.g., an alcohol and an ether with the same formula)
Stereoisomers
  • Atoms are connected in the same order, but differ in their spatial arrangement
  1. Geometric Isomers (“cis-trans” isomers)
    1. Differ in the placement of groups around a rigid structure, typically a double bond or a ring
      • cis: Similar groups are on the same side of the double bond/ring
      • trans: Similar groups are on opposite sides of the double bond/ring
  2. Enantiomers (Optical Isomers)
    1. Molecules that are non-superimposable mirror images of each other (like left and right hands)
    2. Occur in molecules with a chiral center (usually a carbon atom bonded to four different groups)
    3. Have identical physical properties (melting point, boiling point, density) except for their interaction with plane-polarized light and other chiral molecules
    4. Diastereomers: Stereoisomers that are not mirror images of each other. Geometric isomers are a type of diastereomer. Molecules with multiple chiral centers can also have diastereomers

Naming

  • The prefix indicates the number of carbon atoms
  • The ending indicates the functional groups of the structure (C=C “ene”, -OH “ol”)
  • Any branches are indicated BEFORE the prefix

Syntax: BRANCHES # of C’s BONDS FUNCTIONAL GROUPS

Naming branched hydrocarbons

  1. Identify longest continuous chain or ring of carbon atoms
  2. Number the carbons to give the lowest sum for number of branches
  3. Name each branch and indicate its location with a number
  4. List the branches in alphabetical order before the prefix
  5. Comma separate numbers and hyphens to separate numbers from words
  6. If there are more than one of the same branch, Greek prefixes (di, tri, tetra) can be used

Priority Order (highest to lowest): Carboxylic acids > Esters > Amides > Aldehydes > Ketones > Alcohols > Amines > Ethers > Alkenes > Alkynes > Alkanes

Prefixes
  1. Meth (1C)
  2. Eth (2C)
  3. Prop (3C)
  4. But (4C)
  5. Pent (5C)
  6. Hex (6C)
  7. Hept (7C)
  8. Oct (8C)
  9. Non (9C)
  10. Dec (10C)
  11. Undec (11C)
  12. Dodec (12C)

Additional Prefixes For Benzene

  • 1,2 - Ortho (adjacent)
  • 1,3 - Meta (separated by one)
  • 1,4 - Para (opposite)
Alkenes
  • When you have 4 or more carbons you need to show where the double bond is
  • If it has cis or trans configuration that would be indicated before the number
    • This is for the hydrogens: cis is if they are on same side, trans is if on opposite sides
    • For cis line diagrams: Instead of zig-zags you need to go flat for the cis configuration
Alkynes
  • Both double and triple bonds have equal priority. However if the numbering is the same, the smaller value gets the priority
  • In the case where the double and triple bond have the same position number, the double bond gets priority in naming
Organic FamilyNaming RulesExampleGeneral Formula
Alkanesprefix + -anebutaneC₍ₙ₎H₍₂ₙ₊₂₎
Alkenesprefix + -ene (with position number)but-2-ene
Alkynesprefix + -yne (with position number)but-2-yneC₍ₙ₎H₍₂ₙ₋₂₎
Cycloalkanescyclo + prefix + -anecyclobutaneC₍ₙ₎H₍₂ₙ₎

Physical Properties

Organic FamilyFunctional GroupPolar or Non-PolarIntermolecular ForcesPhysical PropertiesNotes
AlkanesC-H bonds onlyNon-polarLDF only• Low BP/MP
• Insoluble in water
• Soluble in non-polar solvents
• BP increases with chain length		Saturated hydrocarbons
AlkenesC=CNon-polar (unless substituted)LDF only• Similar to alkanes
• Slightly lower BP than corresponding alkane
• Insoluble in water		Unsaturated hydrocarbons
AlkynesC≡CNon-polar (unless substituted)LDF only• Similar to alkenes
• Higher BP than corresponding alkene
• Insoluble in water		Unsaturated hydrocarbons
CycloalkanesRing structureNon-polarLDF only• Higher BP than corresponding alkane
• More rigid structure		Ring strain affects stability
AromaticsBenzene RingNon-polar to slightly polarLDF, π-π stacking• Higher BP than alkanes
• Planar structure
• Stable due to resonance		Phenyl if not the main chain
EthersR-O-RSlightly polarLDF, weak dipole-dipole• Lower BP than alcohols
• Some water solubility (small ethers)
• Good solvents		Oxygen creates dipole
AlcoholsR-OHPolarLDF, dipole-dipole, H-bonds• High BP due to H-bonding
• Water soluble (small alcohols)
• Forms H-bonds with water		-OH creates strong polarity
PeroxidesR-O-O-RNon-polar unless R is hydrogenLDF, dipole-dipole/H-bonds if R=H• O-O bond unstable
• Can dissolve in water
• Fire/explosive hazards		Unstable, breaks easily
AldehydesR-CHOPolarLDF, dipole-dipole• Moderate BP
• Small ones water soluble
• Cannot form H-bonds to themselves		C=O creates dipole
KetonesR-CO-RPolarLDF, dipole-dipole• Similar to aldehydes
• Good solvents
• Some water solubility		C=O creates dipole
Carboxylic AcidsR-COOHPolarLDF, dipole-dipole, H-bonds• High BP due to H-bonding
• Water soluble (small ones)
• Can form dimers		Strong H-bond donors/acceptors
EstersR-COO-RPolarLDF, dipole-dipole• Lower BP than corresponding acid
• Pleasant odors
• Limited water solubility		Cannot H-bond to themselves
AminesR-NH₂PolarLDF, dipole-dipole, H-bonds• High BP (but lower than alcohols)
• Water soluble (small ones)
• Basic properties		N can form H-bonds
AmidesR-CO-NH₂PolarLDF, dipole-dipole, H-bonds• Very high BP
• Strong H-bonding
• Water soluble		Both C=O and N-H can H-bond
Benzene
  • Planar molecule
  • The C-C bonds are always the same length and energy which shows that the bonds are not true double/single bonds
  • Exhibits resonance stabilization
  • Bond length is between single and double bond lengths
Alcohols
  1. Primary (1°)
    • -OH is attached to a carbon that is bonded to only one other carbon
    • Example: butan-1-ol (CH₃CH₂CH₂CH₂OH)
  2. Secondary (2°)
    • -OH is attached to a carbon bonded to two other carbons
    • Example: butan-2-ol (CH₃CH(OH)CH₂CH₃)
  3. Tertiary (3°)
    • -OH is attached to a carbon bonded to three other carbons
    • Example: 2-methylpropan-2-ol ((CH₃)₃COH)
Naming Alcohols
  1. Determine the name of the main chain containing the hydroxyl group
  2. Remove the “e” from the end of the main chain and add “ol”
  3. Indicate the number to which the -OH is bonded (starting at 3 carbons)
  4. If you have multiple -OH groups, use Greek prefixes (di, tri, etc.)
  5. Call it “hydroxy” if it’s a branch (not the main functional group)
Ethers

Used as anesthetic

Naming Ethers
  1. The longest carbon chain connected to the oxygen is the base name
  2. Add “oxy” to the end of the prefix for the other carbon chain (e.g., methoxy, propan-2-oxy)
  3. Indicate position with a number
Peroxides

R-O-O-R

  • Very unstable, breaks down into an ether and oxygen gas
Naming Peroxides
  1. Take the two R chains, add “yl” to the end of both in alphabetical order, add “peroxide” at the end
    • Example: butyl ethyl peroxide
Aldehydes and Ketones

Both contain a C=O bond (carbonyl group) Functional isomers of each other

  • Aldehydes: Carbonyl group is attached to an end carbon (terminal)
  • Ketones: Carbonyl group attached anywhere else (internal)
Naming Aldehydes and Ketones
  1. Take longest chain, remove “e” and add “al” for aldehydes or “one” for ketones
  2. Aldehydes have priority over ketones and alcohols
  3. If you have both aldehydes and ketones, use “al” as the suffix and add “oxo” as a branch for the ketone
Carboxylic Acids
  • Contains the carboxyl functional group: R-COOH
  • Highest priority functional group
Naming Carboxylic Acids
  1. Find longest chain containing COOH
  2. Remove the “e” and add “oic acid”
  3. COOH carbon is always carbon #1
Esters

Responsible for tastes and odors Made from an alcohol and a carboxylic acid

Essentially a carboxylic acid with an -R group replacing the H in -COOH

Naming Esters
  1. Use “yl” for the part attached to oxygen (from alcohol)
  2. Other part ends with “oate” (from acid)
  3. Format: alkyl alkanoate
  4. Examples: methyl propanoate, propan-2-yl ethanoate
Amines
  • Contains nitrogen: R-NH₂ (primary), R₂NH (secondary), R₃N (tertiary)
  • Basic compounds (can accept protons)
Naming Amines
  1. Primary amines: prefix + “amine”
  2. For secondary/tertiary: use N- to indicate substituents on nitrogen
  3. Example: N-methylmethanamine
Amides
  • Contains C-N bond with carbonyl: R-CO-NH₂
  • Very stable due to resonance
Naming Amides
  1. Find longest chain containing CO-NH₂
  2. Remove “e” and add “amide”
  3. For N-substituted amides, use N- prefix

Reactions

Combustion

All families will undergo combustion since they contain carbon and hydrogen

Complete Combustion: Organic + O₂ → CO₂ + H₂O Incomplete Combustion: Organic + O₂ → CO + CO₂ + H₂O + C (soot)

Substitution

An atom or group on the chain is replaced with another Require energy to occur, conditions matter

  1. Alkanes

    • With: Halogen (Cl₂, Br₂)
    • Catalyst: UV light
    • Products: Haloalkane + hydrogen halide
    • Example: CH₄ + Cl₂ → CH₃Cl + HCl

  2. Aromatics

    • With: Halogens

    • Catalyst: FeBr₃ or FeCl₃

    • Products: Halobenzene + hydrogen halide

    • With: Nitric Acid (HNO₃)

    • Catalyst: Sulfuric acid (H₂SO₄)

    • Products: Nitrobenzene + water

  3. Alcohols

    • With: Hydrogen halide (HX)
    • Catalyst: ZnCl₂ (Lucas reagent)
    • Products: Alkyl halide + water
    • Notes: Always replaces the -OH group

  4. Ethers (R-O-R)

    • With: 2 equivalents of hydrogen halide
    • Catalyst: Heat (Δ)
    • Products: 2 alkyl halides + water
    • Notes: Splits the ether at both sides of oxygen

  5. Amines

    • With: Alkyl halide
    • Catalyst: None needed
    • Products: Higher amine + hydrogen halide

Addition Reactions

Occur with unsaturated compounds (alkenes, alkynes)

  1. Hydrogenation: C=C + H₂ → C-C (with catalyst like Pd, Pt, or Ni)
  2. Halogenation: C=C + X₂ → C-C with X on each carbon
  3. Hydrohalogenation: C=C + HX → C-C with H and X added (follows Markovnikov’s rule)

Markovnikov’s Rule: When HX adds to an alkene, H goes to the carbon with more hydrogens already attached.

Elimination Reactions

Remove atoms/groups to form double/triple bonds

  1. Dehydration of Alcohols: Alcohol + H₂SO₄ + heat → Alkene + H₂O
  2. Dehydrohalogenation: Alkyl halide + strong base → Alkene + HX

Oxidation Reactions

  1. Primary Alcohols:
    • Mild oxidation → Aldehyde
    • Strong oxidation → Carboxylic acid
  2. Secondary Alcohols: → Ketones
  3. Tertiary Alcohols: No reaction under normal conditions

Esterification

Carboxylic Acid + Alcohol ⇌ Ester + Water

  • Requires acid catalyst (H₂SO₄)
  • Reversible reaction
  • Remove water to drive reaction forward

Key Concepts

VBT (Valence Bond Theory)

  • Explains bonding through overlap of atomic orbitals
  • Bonds form when orbitals overlap and share electrons
  • Different from molecular orbital theory

Sigma vs Pi Bonds

  • Sigma (σ) bonds: Head-to-head orbital overlap, strongest bonds, allow rotation
  • Pi (π) bonds: Side-to-side orbital overlap, weaker, restrict rotation
  • Single bonds = 1σ, Double bonds = 1σ + 1π, Triple bonds = 1σ + 2π

Hybridization

  • sp³: Tetrahedral geometry (109.5°), found in alkanes
  • sp²: Trigonal planar geometry (120°), found in alkenes
  • sp: Linear geometry (180°), found in alkynes
  • Hybrid orbitals explain molecular geometry and bonding

Network Solids

  • Examples: Diamond, graphite, quartz
  • Have the highest melting points due to extensive covalent bonding throughout the structure
  • Very hard and often insoluble

Practice

  • 1-bromo-3-methylcyclobutane

  • 1-chloro-2,4-dimethylcyclopentane

  • 4-methylhex-trans-2-ene

  • 3-methylhex-cis-4-trans-2-diene

  • 3-ethylcyclopent-1-ene

  • 7-methyl-3-propan-2-yldec-5-yne

  • 6-bromo-3,4-dimethylhept-cis-5-en-1-yne

  • propoxybenzene

  • 2-methoxyhexane

  • 5,6-dichlorohept-trans-5-en-2-one

  • 6-hydroxyhexan-2-one

  • 4-hydroxypentanoic acid

  • 3-chloro-4-methylpentanoic acid

Graph View