From the following, the least stable structure is :

Solution & Explanation

### Core Logic In structure 3, there are positive formal charges on two adjacent atoms (Oxygen and the Carbon adjacent to it). Like charges on adjacent atoms cause extreme electrostatic repulsion, making the structure highly unstable.
Resonance Effects diagram for Q62 - JEE Main 2026 Morning
Resonance Effects diagram for Q62 - JEE Main 2026 Morning
### Pattern Recognition Rules of resonance stability: 1. Complete octets are more stable. 2. More covalent bonds = more stable. 3. Least charge separation is more stable. 4. Like charges on adjacent atoms create massive destabilization (Least stable scenario). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques

Reference Study Guides

Organic Chemistry Some Basic Principles And Techniques

More Organic Chemistry - Some Basic Principles and Techniques Previous-Year Questions — Page 10

Q34 jee_main_2025_24_jan_morning Quantitative Analysis of Organic Compounds
Given below are two statements I and II. Statement I: Dumas method is used for estimation of "Nitrogen" in an organic compound. Statement II: Dumas method involves the formation of ammonium sulphate by heating the organic compound with conc mathrmH_2mathrmSO_4 In the light of the above statements, choose the correct answer from the options given below
  • A. Both Statement I and Statement II are true.
  • B. Statement I is false but Statement II is true
  • C. Both Statement I and Statement II are false.
  • D. Statement I is true but Statement II is false

Solution

### Core Logic Statement I is fully accurate: Dumas method is standardly applied for estimating elemental nitrogen across structural compounds. Statement II is incorrect: The reaction leading to ammonium sulphate generation by intense thermal heating alongside concentrated mathrmH_2mathrmSO_4 describes the **Kjeldahl method**, not the Dumas strategy. The Dumas process instead relies on burning carbonaceous compounds explicitly with copper oxide to convert nitrogen cleanly into free gas (N_2). ### Pattern Recognition Dumas method collects element gas N_2 via volumetric analysis; Kjeldahl maps digestions via standard (mathrmNH_4)_2mathrmSO_4 pathways. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q31 jee_main_2025_28_jan_evening Purification of Organic Compounds
The purification method based on the following physical transformation is : textSolid xrightarrow[(textX)]textHeat textVapour xrightarrow[(textX)]textCool textSolid
  • A. Sublimation
  • B. Distillation
  • C. Crystallization
  • D. Extraction

Solution

### Related Formula Direct phase transition without passing through an intermediate liquid phase defines sublimation: textSolid rightleftharpoons textVapour ### Core Logic The schematic diagram represents a solid turning directly into vapor on heating, which then reverts back to a solid phase upon cooling. This distinct behavior isolates sublimable solids from non-sublimable impurities. ### Step 1: Identification This transformation perfectly defines the laboratory purification process known as **Sublimation**. ### Pattern Recognition Look for the skipping of the liquid state entirely: Solid rightarrow Vapour rightarrow Solid. Common examples include camphor, naphthalene, benzoic acid, and iodine. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q44 jee_main_2025_28_jan_evening Isomerism
Given below are two statements: Statement (I): Oxacyclobutane and prop-2-en-1-ol are isomeric compounds. Statement (II): Propan-1-amine and N-methylethanamine are functional group isomers. In the light of the above statements, choose the correct answer from the options given below :
  • A. Both Statement I and Statement II are false
  • B. Both Statement I and Statement II are true
  • C. Statement I is true but Statement II is false
  • D. Statement I is false but Statement II is true

Solution

### Related Formula Isomers share an identical molecular formula but differ in structural arrangement or functional groups: textSame M_f neq textSame structural layout ### Core Logic Evaluating the structural parameters: - **Statement I**: Oxacyclobutane (a cyclic ether) and prop-2-en-1-ol (an unsaturated alcohol) both possess the molecular formula C_3H_6O. They are functional/ring-chain isomers, so Statement I is true. - **Statement II**: Propan-1-amine (1^circ amine) and N-methylethanamine (2^circ amine) both share the molecular formula C_3H_9N. Because primary, secondary, and tertiary amines contain different functional groups, they act as functional group isomers. Thus, Statement II is true. ### Step 1: Conclusion Match Since both structural statements are valid, both Statement I and Statement II are true.
Skeletal representations for the specified organic isomers
Skeletal representations for the specified organic isomers
### Pattern Recognition Always remember that 1^circ, 2^circ, and 3^circ amines are classified as *different functional groups* in IUPAC nomenclature. Consequently, structural shifts between them with a constant carbon count represent functional group isomerism. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q jee_main_2025_29_jan_morning Nucleophiles and Electrophiles
Total number of nucleophiles from the following is :- mathrm N H _ 3, mathrm P h S H, (mathrm H _ 3 mathrm C) _ 2 mathrm S, mathrm H _ 2 mathrm C = mathrm C H _ 2, stackrel ominus mathrm O mathrm H, mathrm H _ 3 mathrm O ^ oplus, (mathrm C H _ 3) _ 2 mathrm C O, > = mathrm N C H _ 3
  • A. 5
  • B. 4
  • C. 7
  • D. 6

Solution

### Related Formula Nucleophiles are electron-rich species containing lone pairs of electrons or pi-bonds that can donate an electron pair to an electrophilic center. ### Core Logic Let us examine each species: * mathrmNH_3: Contains a lone pair on nitrogen rightarrow Nucleophile * mathrmPhSH: Contains lone pairs on sulfur rightarrow Nucleophile * (mathrmH_3mathrmC)_2mathrmS: Contains lone pairs on sulfur rightarrow Nucleophile * mathrmH_2mathrmC=mathrmCH_2: Contains a nucleophilic pi-bond rightarrow Nucleophile * stackrelominusmathrmOmathrmH: Negatively charged with lone pairs rightarrow Nucleophile * mathrmH_3mathrmO^oplus: Electron deficient, positively charged oxygen cannot donate electrons rightarrow Electrophile * (mathrmCH_3)_2mathrmCO: Carbonyl carbon is electrophilic * >=mathrmNCH_3: Imine carbon is electrophilic Thus, the total number of nucleophiles is 5. ### Pattern Recognition Neutral molecules with lone pairs (N, S) or alkenes/alkynes with available pi-electrons operate as good nucleophiles, along with full anions. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q jee_main_2025_29_jan_morning IUPAC Nomenclature of Organic Compounds
Match List-I with List-II. Choose the correct answer from the options given below:
IUPAC Nomenclature of Organic Compounds
IUPAC Nomenclature of Organic Compounds
  • A. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
  • B. (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
  • C. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
  • D. (A)-(II), (B)-(III), (C)-(I), (D)-(IV)

Solution

### 1. RELATED FORMULA IUPAC Rules select the longest principal carbon chain and number it to give substituents the lowest possible locants. ### 2. EXECUTION **CORE LOGIC** Let's systematic decode each name : * (A) Longest chain contains 7 carbons (heptane) with an ethyl group at position 3 and a methyl group at position 5 rightarrow 3-Ethyl-5-methylheptane (II) . * (B) C expanded yields a 7 carbon main chain with two methyl groups at carbon-4 rightarrow 4,4-Dimethylheptane (III) . * (C) 5-carbon diene numbered from the left double bond side rightarrow 2-Methyl-1,3-pentadiene (IV) . * (D) 5-carbon alkene starting from the double bond end rightarrow 4-Methylpent-1-ene (I) . Therefore, matching sequence: (A)-(II), (B)-(III), (C)-(IV), (D)-(I). ### 3. PATTERN RECOGNITION Expanding compressed groupings such as mathrm(C_3H_7)_2 prevents errors regarding parent chain carbon counts. ### 4. EVALUATION RUBRIC / MODEL ANSWER null ### 5. CHAPTER MIX Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques

More Organic Chemistry - Some Basic Principles and Techniques Questions — jee_main_2026_21_jan_morning

Practice all Organic Chemistry - Some Basic Principles and Techniques previous-year questions →

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)
YOUR FIRST PREP STEP STARTS HERE

We Map Every Repeating Question in Competitive Exams.

Say goodbye to generic mock test fatigue. RankBit uses smart analysis to group past exam questions into their foundational Repeating Question Types. Find chapter weightage, track repeating questions, and score higher with targeted practice.

Select Your Target Exam

Choose an exam track below to find formulas per chapter and patterns.

Syncing Exam Intelligence

Mapping formulas and patterns across all tracks…

PATH A — FULL LENGTH PRACTICE

Full Mock Test Hub

Simulate real NTA exam conditions with fully tracked mocks. Time yourself against past papers.

Now Live Open
PATH B — TARGETED PRACTICE

Topic-wise Practice Hub

Practice past-year questions one chapter at a time. Pick an exam → subject → chapter and get every PYQ for that topic — pulled together from all past papers — with the chapter's key formulas alongside.

Loading Questions... Browse Topics

Exam Analysis Tools

Chapter weightage trends and topic-wise practice — all mapped from past shift papers.

Year-wise PYQ

Chapter Weightage & Trends

See high-yield chapters, year-wise counts and the frequency-based chance each topic repeats next exam.

Weightage Board Open
Targeted PYQs

Topic-wise Practice Hub

Every past-year question for a chapter pulled from all papers, with its key formulas alongside.

One chapter at a time Open
Latest from the Blog
View all →

Loading articles...