GATE Life Sciences Structure-Reactivity Correlations and Organic Reaction Mechanisms Syllabus

Structure-Reactivity Correlations and Organic Reaction Mechanisms syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Structure-Reactivity Correlations and Organic Reaction Mechanisms in GATE Life Sciences, not a summary of it.

1. 1

   Acids and Bases

   2 topics

   • Electronic Effects
   • Steric Effects
2. 2

   Stereochemistry

   2 topics

   • Optical Isomerism
   • Geometrical Isomerism
3. 3

   Tautomerism

   1 topic

   • Conformers
4. 4

   Aromaticity

   overview

   Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

5. 5

   Elementary Treatment of Organic Reaction Mechanisms

   5 topics

   • SN1 Reactions
   • SN2 Reactions
   • E1 Reactions
   • E2 Reactions
   • Radical Reactions
6. 6

   Hoffmann/Saytzeff Rules

   overview

   Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

7. 7

   Addition Reactions

   overview

   Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

8. 8

   Markownikoff Rule

   overview

   Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

9. 9

   Kharasch Effect

   overview

   Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

10. 10

    Elementary Hydroboration Reactions

    overview

    Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

11. 11

    Grignard's Reagents and Their Uses

    overview

    Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

12. 12

    Aromatic Electrophilic Substitutions

    1 topic

    • Orientation Effect
      • Exemplified by Various Functional Groups
13. 13

    Identification of Common Functional Groups by Chemical Tests

    overview

    Examined as a single unit within Structure-Reactivity Correlations and Organic Reaction Mechanisms — no further topic split in the official outline.

Structure-Reactivity Correlations and Organic Reaction Mechanisms flashcards for GATE Life Sciences

18 of 50 cards from the Structure-Reactivity Correlations and Organic Reaction Mechanisms deck — real questions with worked answers.

1. What is the inductive effect ($I$ effect) in organic chemistry?

   The permanent polarization of a $\sigma$-bond due to electronegativity differences, causing partial charges that are transmitted through the carbon chain and diminish with distance ($\approx$ negligible beyond 3 carbons).

2. Distinguish the $+I$ effect from the $-I$ effect, giving an example group of each.

   $+I$ (electron-donating, e.g. alkyl groups like $\ce{-CH3}$, $\ce{-CH2CH3}$) push electron density toward the chain; $-I$ (electron-withdrawing, e.g. $\ce{-NO2}$, $\ce{-CN}$, halogens) pull electron density away.

3. Arrange these groups in order of increasing $-I$ effect: $\ce{-NR3+}$, $\ce{-F}$, $\ce{-OR}$, $\ce{-COOH}$.

   $\ce{-OR} < \ce{-COOH} < \ce{-F} < \ce{-NR3+}$. Positively charged and more electronegative atoms exert stronger electron withdrawal.

4. What is the resonance (mesomeric, $M$) effect?

   Delocalization of $\pi$-electrons or lone pairs through conjugated systems, producing permanent polarization. $+M$ groups donate electrons into the system (e.g. $\ce{-OH}$, $\ce{-NH2}$); $-M$ groups withdraw (e.g. $\ce{-NO2}$, $\ce{-C=O}$).

5. How does the inductive effect explain the increasing acidity of chloroacetic acids: acetic, chloroacetic, dichloroacetic, trichloroacetic?

   Each electronegative $\ce{Cl}$ exerts a $-I$ effect that stabilizes the carboxylate anion, increasing acidity. Thus $pK_a$ order: $\ce{CH3COOH} (4.76) > \ce{ClCH2COOH} (2.86) > \ce{Cl2CHCOOH} (1.29) > \ce{Cl3CCOOH} (0.65)$.

6. What is hyperconjugation and what structural requirement does it need?

   Delocalization of $\sigma$ (C–H) bonding electrons into an adjacent empty or partially filled $p$-orbital or $\pi$-system ("no-bond resonance"). It requires $\alpha$-hydrogens on carbon adjacent to the unsaturation/cation.

7. Why is the order of carbocation stability $3° > 2° > 1° > \ce{CH3+}$?

   Increasing alkyl substitution provides more $+I$ (inductive electron donation) and more $\alpha$-C–H bonds for hyperconjugation, both of which stabilize the electron-deficient cation.

8. What is the steric effect and how does it differ from electronic effects?

   The steric effect arises from spatial/volume repulsion between bulky groups (van der Waals strain), independent of electron-density transmission. Electronic effects act through bonds/orbitals, whereas steric effects act through space.

9. Define steric inhibition of resonance with an example.

   When bulky ortho substituents force a group out of the plane of a conjugated system, preventing effective $p$-orbital overlap and reducing resonance. Example: 2,6-disubstituted $N,N$-dimethylaniline shows weakened lone-pair conjugation with the ring.

10. What is B-strain (back strain) and F-strain (front strain)?

    B-strain: steric strain relieved when a sp$^3$ center bearing bulky groups rehybridizes (e.g. amine basicity changes). F-strain: strain at the front of an approaching reagent that hinders bonding to a crowded reaction center.

11. State the two necessary and sufficient conditions for a molecule to be chiral.

    The molecule must be non-superimposable on its mirror image. The standard test: it possesses no improper axis of symmetry ($S_n$), i.e. no plane of symmetry ($\sigma$), no center of inversion ($i$), and no $S_n$ axis.

12. Define enantiomers and diastereomers.

    Enantiomers are non-superimposable mirror-image stereoisomers (identical physical properties except optical rotation sign and chiral interactions). Diastereomers are stereoisomers that are not mirror images and differ in physical/chemical properties.

13. How many stereoisomers are possible for a molecule with $n$ stereocenters, and what is the exception?

    A maximum of $2^{n}$ stereoisomers. The number is fewer than $2^{n}$ when internal symmetry creates meso compounds (which reduce the count due to a plane of symmetry).

14. What is a meso compound?

    A molecule containing stereocenters yet achiral overall because an internal plane of symmetry makes it superimposable on its mirror image (e.g. meso-tartaric acid). It is optically inactive (internal compensation).

15. State the priority rules used to assign $R$/$S$ configuration (CIP rules).

    Rank the four groups by Cahn–Ingold–Prelog priority (higher atomic number = higher priority; explore outward at first point of difference; treat double bonds as duplicated atoms). View with lowest priority pointing away; clockwise $1{\to}2{\to}3$ = $R$, counterclockwise = $S$.

16. What is specific rotation and give its defining equation.

    Specific rotation $[\alpha]_{\lambda}^{T}$ characterizes a chiral substance's optical activity: $$[\alpha]_{\lambda}^{T} = \frac{\alpha}{l \cdot c}$$ where $\alpha$ is observed rotation (degrees), $l$ is path length (dm), and $c$ is concentration (g/mL).

17. Define enantiomeric excess (ee) and give its formula.

    Enantiomeric excess measures purity of one enantiomer over the racemate: $$\mathrm{ee} = \frac{|[R] - [S]|}{[R] + [S]} \times 100\%$$ It equals the percent of the major enantiomer minus the minor.

18. What is a racemic mixture and what is its net optical rotation?

    A racemic mixture (racemate) is a 1:1 mixture of two enantiomers; its net optical rotation is zero (external compensation), denoted ($\pm$) or $dl$.

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