General Organic Chemistry Formulas For JEE 2026, Download PDF

Types of Hybridization in Carbon

Ways to Represent Organic Molecules

• Molecular formula — shows only the types and numbers of atoms. E.g., C$$_2$$H$$_6$$O.
• Structural formula — shows every bond explicitly. All atoms and all bonds are drawn.
• Condensed formula — atoms are grouped but not all bonds are shown. E.g., CH$$_3$$CH$$_2$$OH.
• Bond-line (skeletal) formula — carbon skeleton drawn as a zigzag line. Each vertex and endpoint represents a carbon. Hydrogen atoms on carbon are implied. Heteroatoms (O, N, etc.) are written explicitly.

Important Functional Groups for JEE

Steps for IUPAC Naming

• Step 1: Find the longest continuous carbon chain that includes the principal functional group. This gives the root word.
• Step 2: Number the chain from the end that gives the lowest locant to the principal functional group.
• Step 3: Identify substituents (branches) and name them with their position numbers.
• Step 4: Combine: substituent positions + substituent names (alphabetical) + root word + suffix.

Root Words for Carbon Chain Length

Types of Structural Isomerism

• Chain isomerism — different carbon skeletons (straight vs. branched). E.g., C$$_4$$H$$_{10}$$: butane vs. 2-methylpropane (isobutane).
• Position isomerism — same functional group at different positions on the chain. E.g., C$$_3$$H$$_7$$OH: propan-1-ol vs. propan-2-ol.
• Functional group isomerism — different functional groups with the same formula. E.g., C$$_2$$H$$_6$$O: ethanol (CH$$_3$$CH$$_2$$OH) vs. dimethyl ether (CH$$_3$$OCH$$_3$$).
• Metamerism — same functional group but different alkyl groups on either side. E.g., C$$_4$$H$$_{10}$$O: diethyl ether (C$$_2$$H$$_5$$OC$$_2$$H$$_5$$) vs. methyl propyl ether (CH$$_3$$OC$$_3$$H$$_7$$).

Geometrical (Cis-Trans / E-Z) Isomerism

Occurs when there is restricted rotation (typically around a C=C double bond) and each doubly-bonded carbon has two different groups attached.

• Cis (Z) — higher-priority groups on the same side of the double bond.
• Trans (E) — higher-priority groups on opposite sides.
• The E/Z system uses Cahn-Ingold-Prelog (CIP) priority rules: higher atomic number = higher priority. If the two higher-priority groups are on the same side → Z (zusammen = together); opposite side → E (entgegen = opposite).

Condition for geometrical isomerism: Both doubly-bonded carbons must carry two different groups each.

• Chiral centre (stereocentre): A carbon atom bonded to four different groups. Such a carbon is called an asymmetric carbon and is marked with an asterisk (*).
• A molecule with a chiral centre is non-superimposable on its mirror image, just like your left and right hands.
• Enantiomers: A pair of molecules that are mirror images of each other but cannot be superimposed. They have identical physical properties except they rotate plane-polarised light in opposite directions.
• Diastereomers: Stereoisomers that are NOT mirror images of each other. They have different physical properties.
• R/S Configuration (CIP rules): Assign priority 1 > 2 > 3 > 4 to the four groups by atomic number. Orient the molecule so group 4 points away from you. If the sequence 1 → 2 → 3 goes clockwise → R (rectus); anticlockwise → S (sinister).

Inductive Effect

• $$-$$I effect (electron-withdrawing): The substituent pulls electron density away from the chain.
  Order: $$\text{--NO}_2 > \text{--CN} > \text{--F} > \text{--Cl} > \text{--Br} > \text{--I} > \text{--OH} > \text{--OCH}_3$$
• $$+$$I effect (electron-donating): The substituent pushes electron density into the chain.
  Order: $$\text{--C(CH}_3\text{)}_3 > \text{--CH(CH}_3\text{)}_2 > \text{--CH}_2\text{CH}_3 > \text{--CH}_3 > \text{--H}$$
• The inductive effect decreases rapidly along the chain (practically negligible beyond 3–4 bonds).

Mesomeric Effect

• $$+$$M effect (electron-donating by resonance): Groups that donate electron density into the $$\pi$$ system via their lone pair.
  Groups: –NH$$_2$$, –NHR, –OH, –OR, –X (halogens)
• $$-$$M effect (electron-withdrawing by resonance): Groups that withdraw electron density from the $$\pi$$ system via multiple bonds to electronegative atoms.
  Groups: –NO$$_2$$, –CN, –CHO, –COOH, –COR, –SO$$_3$$H

Hyperconjugation

• Occurs when a C–H bond is adjacent to a positively charged carbon, a double bond, or a radical centre.
• The number of hyperconjugative structures = number of $$\alpha$$-hydrogen atoms (H atoms on the carbon next to the functional site).
• More $$\alpha$$-hydrogens → more hyperconjugation → greater stabilization.

Classification of Reagents

• Electrophile ("electron-loving"): A species that accepts an electron pair. It is electron-deficient.
  Examples: H$$^+$$, NO$$_2^+$$, Br$$^+$$, AlCl$$_3$$, BF$$_3$$, carbocations (R$$^+$$)
• Nucleophile ("nucleus-loving"): A species that donates an electron pair. It is electron-rich.
  Examples: OH$$^-$$, CN$$^-$$, NH$$_3$$, H$$_2$$O, Cl$$^-$$, carbanions (R$$^-$$)
• Free radical: A species with an unpaired electron. It is electrically neutral but highly reactive.
  Examples: Cl$$\cdot$$, Br$$\cdot$$, CH$$_3\cdot$$

Four Main Types of Organic Reactions

• Substitution: One atom or group is replaced by another. $$$\text{R--X} + \text{Y}^- \longrightarrow \text{R--Y} + \text{X}^-$$$
• Addition: Two reactants combine to form a single product (a $$\pi$$ bond breaks and two new $$\sigma$$ bonds form). $$$\text{C=C} + \text{X--Y} \longrightarrow \text{X--C--C--Y}$$$
• Elimination: A single reactant loses atoms/groups to form a $$\pi$$ bond (opposite of addition). $$$\text{X--C--C--H} \longrightarrow \text{C=C} + \text{HX}$$$
• Rearrangement: Atoms within a molecule shift positions to form a structural isomer. E.g., 1,2-hydride shift, 1,2-methyl shift in carbocation intermediates.

Carbocation Stability Order

$$$3° > 2° > 1° > \text{CH}_3^+$$$

$$$(CH_3)_3C^+ > (CH_3)_2CH^+ > CH_3CH_2^+ > CH_3^+$$$

Reason: Alkyl groups stabilize the positive charge through hyperconjugation and the +I effect.

Special stable carbocations:

• Allylic: CH$$_2$$=CH–CH$$_2^+$$ (resonance-stabilized)
• Benzylic: C$$_6$$H$$_5$$CH$$_2^+$$ (resonance-stabilized)
• Tropylium: C$$_7$$H$$_7^+$$ (aromatic, 6$$\pi$$ electrons)

Carbanion Stability Order

$$$\text{CH}_3^- > 1° > 2° > 3°$$$

Reason: Alkyl groups are electron-donating (+I effect), which destabilizes the negative charge. Fewer alkyl groups → more stable carbanion.

Note: This is the opposite of carbocation stability.

Stabilizing factors: Electron-withdrawing groups ($$-$$I, $$-$$M) near the carbanion increase stability. Resonance delocalization also helps (e.g., allylic, benzylic carbanions).

Free Radical Stability Order

$$$3° > 2° > 1° > \text{CH}_3\cdot$$$

Reason: Hyperconjugation stabilizes radicals, similar to carbocations. Allylic and benzylic radicals are extra stable due to resonance.

Factors Affecting Acidity

• Electronegativity: Across a period, acidity increases as the atom bonded to H becomes more electronegative.
  $$\text{CH}_4 < \text{NH}_3 < \text{H}_2\text{O} < \text{HF}$$
• Size of atom: Down a group, acidity increases as the conjugate base spreads charge over a larger orbital.
  $$\text{HF} < \text{HCl} < \text{HBr} < \text{HI}$$
• Electron-withdrawing groups ($$-$$I, $$-$$M): Stabilize the conjugate base → increase acidity.
  $$\text{CH}_3\text{COOH} < \text{ClCH}_2\text{COOH} < \text{Cl}_2\text{CHCOOH} < \text{Cl}_3\text{CCOOH}$$
• Electron-donating groups ($$+$$I, $$+$$M): Destabilize the conjugate base → decrease acidity.
• Resonance stabilization of conjugate base: If the anion is resonance-stabilized, the acid is stronger. Carboxylic acids (R–COOH) are stronger than alcohols (R–OH) because the carboxylate anion (RCOO$$^-$$) has two equivalent resonance structures.
• s-character: More s-character in the orbital holding the lone pair of the conjugate base → electrons held closer to nucleus → more stable anion → stronger acid. Acidity of C–H bonds: $$sp > sp^2 > sp^3$$.

Factors Affecting Basicity

• Basicity is related to how readily a species donates its lone pair to accept a proton.
• Electron-donating groups (+I) on nitrogen increase basicity of amines.
• Resonance that delocalizes the lone pair decreases basicity. E.g., aniline (C$$_6$$H$$_5$$NH$$_2$$) is less basic than cyclohexylamine because the lone pair on N in aniline is delocalized into the ring.
• Hybridization: $$sp^3 > sp^2 > sp$$ in basicity (more s-character holds the lone pair tighter, making it less available for donation).