Consider the following compound (X) beginarrayc mathrm I \\ mathrm H - mathrm C equiv mathrm C - mathrm C H _ 2 - mathrm C H - mathrm C H _ 3 \\ mathrm I \\ mathrm C H _ 3 endarray The most stable and least stable carbon radicals, respectively, produced by homolytic cleavage of corresponding mathrmC - H bond are :

Solution & Explanation

### Related Formula Free radical stability structural hierarchy sequence: textResonance Stabilized (Propargyl/Allyl) > 3^circ > 2^circ > 1^circ > textVinylic/Alkyne Center ### Core Logic Let's analyze individual cleavage points across the carbon backbone skeleton: * **Position II** yields a propargyl intermediate radical directly adjacent to the alkyne bond. This allows strong resonance stabilization across the pi system, making it the most stable radical position. * **Position I** places the radical directly on an mathrmsp-hybridized carbon center. The high electronegativity of mathrmsp orbitals tightly holds the unpaired electron, making homolytic cleavage extremely difficult and rendering this intermediate the least stable radical position.
Free Radical Stability
Free Radical Stability
### Step 1: Verdict Therefore, the most stable and least stable positions are II and I, respectively. ### Pattern Recognition Radicals located on mathrmsp carbons (vinylic/alkynic) are highly unstable due to poor orbital overlap, while positions next to triple bonds (propargylic) are exceptionally stable due to active resonance delocalization. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques

More Organic Chemistry - Some Basic Principles and Techniques Previous-Year Questions — Page 15

Q65 jee_main_2024_30_jan_morning Aromaticity
Which of the following molecule/species is most stable?
  • A.
  • B.
  • C. textOption 3
  • D. textOption 4

Solution

### Core Logic Stability of cyclic carbocations can be determined using Huckel's rule for aromaticity. A species is exceptionally stable if it is aromatic. Aromaticity requires the system to be cyclic, planar, fully conjugated, and possess (4n + 2) pi electrons. ### Step 1: Analyze Option 1 The tropylium cation (Option 1) is a 7-membered ring with 3 double bonds and a positive charge in continuous conjugation.
Aromaticity solution diagram for Q65 - JEE Main 2024 Morning
Aromaticity solution diagram for Q65 - JEE Main 2024 Morning
Number of pi electrons = 6. Since 6 satisfies (4n+2) for n=1, it is aromatic and therefore highly stable. ### Pattern Recognition Tropylium ion (C_7H_7^+) is a classic example of a stable aromatic carbocation. It frequently appears in stability comparison questions. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q79 jee_main_2024_30_jan_morning Qualitative Analysis of Organic Compounds
The Lassiagne's extract is boiled with dil. HNO_3 before testing for halogens because,
  • A. textAgCN is soluble in HNO_3
  • B. textSilver halides are soluble in HNO_3
  • C. Ag_2Stext is soluble in HNO_3
  • D. Na_2Stext and NaCN are decomposed by HNO_3

Solution

### Core Logic In Lassaigne's test for halogens, we add AgNO_3 to form a precipitate of silver halide (AgX). However, if the organic compound also contains Nitrogen or Sulphur, the Lassaigne's extract will contain NaCN or Na_2S. ### Step 1: Reason for adding HNO3 These ions (CN^- and S^2-) would also react with AgNO_3 to form precipitates (AgCN - white, Ag_2S - black), which would interfere with the test for halogens. Boiling the extract with concentrated/dilute HNO_3 decomposes the cyanide and sulphide to HCN and H_2S gases, which escape, thus removing the interference. NaCN + HNO_3 rightarrow NaNO_3 + HCN uparrow Na_2S + 2HNO_3 rightarrow 2NaNO_3 + H_2S uparrow ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q86 jee_main_2024_30_jan_morning Chromatography
On a thin layer chromatographic plate, an organic compound moved by 3.5text cm, while the solvent moved by 5text cm. The retardation factor of the organic compound is ________ times 10^-1
Numerical Answer. Answer: 7 to 7

Solution

### Related Formula R_f = fractextDistance travelled by compoundtextDistance travelled by solvent ### Step 1: Substitution and calculation R_f = frac3.55 R_f = 0.7 R_f = 7 times 10^-1 ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q75 jee_main_2024_31_jan_evening Purification of Organic Compounds
The fragrance of flowers is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in vapour phase. A suitable method for the extraction of these oils from the flowers is -
  • A. text1. crystallisation
  • B. text2. distillation under reduced pressure
  • C. text3. distillation
  • D. text4. steam distillation

Solution

### Core Logic Steam distillation technique is applied to separate substances which are steam volatile and are immiscible with water. Since the essential oils in flowers are steam volatile and insoluble in water, steam distillation is the perfect technique for their extraction. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q66 jee_main_2024_31_jan_morning Reaction Intermediates
A species having carbon with sextet of electrons and can act as electrophile is called
  • A. textcarbon free radical
  • B. textcarbanion
  • C. textcarbocation
  • D. textpentavalent carbon

Solution

### Core Logic
Reaction Intermediates diagram for Q66 - JEE Main 2024 Morning
Reaction Intermediates diagram for Q66 - JEE Main 2024 Morning
A carbocation has three bonds and an empty p-orbital, yielding a sextet (6) of electrons in its valence shell. Due to its electron deficiency, it acts as a strong electrophile. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
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