### Core Logic By definition, a resonance hybrid (the actual structure) is always more stable than any of its contributing canonical structures (resonance structures). The difference in potential energy between the most stable contributing resonance structure and the actual resonance hybrid is called the resonance energy. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry Some Basic Principles and Techniques

### Core Logic In the Lassaigne's test for elemental analysis, if an organic compound contains both Nitrogen and Sulphur together, the sodium fusion extract contains sodium thiocyanate (NaSCN$NaSCN$) instead of sodium cyanide (NaCN$NaCN$) and sodium sulphide (Na_2S$Na_2S$). Na + C + N + S rightarrow NaSCN$Na + C + N + S \rightarrow NaSCN$ When this extract is treated with Iron (II) sulphate (FeSO_4$FeSO_4$) and acidified with concentrated H_2SO_4$H_2SO_4$ (which oxidizes some Fe^2+$Fe^{2+}$ to Fe^3+$Fe^{3+}$), the Fe^3+$Fe^{3+}$ ions react with the thiocyanate ions to form a blood-red colored complex. ### Step 1: The Reaction Fe^2+ xrightarrow[textConc. H_2SO_4, H^+ Fe^3+$Fe^{2+} \xrightarrow[\text{Conc. } H_2SO_4, {H^+} Fe^{3+}$ Fe^3+ + 3SCN^- rightarrow Fe(SCN)_3 quad text(blood red colour)$Fe^{3+} + 3SCN^- \rightarrow Fe(SCN)_3 \quad \text{(blood red colour)}$ The appearance of the blood red colour specifically confirms the simultaneous presence of both Nitrogen and Sulphur. ### Pattern Recognition N alone rightarrow$\rightarrow$ Prussian Blue (Fe_4[Fe(CN)_6]_3$Fe_4[Fe(CN)_6]_3$). S alone rightarrow$\rightarrow$ Purple colour with sodium nitroprusside or black ppt of PbS$PbS$. N + S together rightarrow$\rightarrow$ Blood red colour (Fe(SCN)_3$Fe(SCN)_3$). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry Some Basic Principles and Techniques

### Core Logic Resonance (or mesomeric effect) occurs when there is a continuous overlap of parallel p-orbitals. This can happen between a pi$\pi$ bond and an adjacent atom holding a lone pair of electrons (e.g., in vinyl chloride CH_2=CH-ddotCl$CH_2=CH-\ddot{C}l$ or aniline Ph-ddotNH_2$Ph-\ddot{N}H_2$). The delocalization of these electrons stabilizes the molecule and is referred to as the resonance effect. ### Step 1: Differentiating the Effects - **Hyperconjugation**: Interaction between sigma$\sigma$ bonds (like C-H$C-H$) and adjacent empty or partially filled p-orbitals or pi$\pi$ bonds. - **Inductive effect**: Polarization of electron density through sigma$\sigma$ bonds due to electronegativity differences. - **Electromeric effect**: Temporary complete transfer of shared pi$\pi$ electron pair to one of the atoms joined by a multiple bond, occurring only at the demand of an attacking reagent. - **Resonance effect**: Delocalization of pi$\pi$ electrons and lone pairs. Thus, the correct answer is resonance. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry Some Basic Principles and Techniques

### Core Logic Differential Extraction is based on the principle of differential solubility of an organic compound in two immiscible solvents (usually water and an organic solvent). Different layers are formed which can be separated using a separating funnel. ### Pattern Recognition Keyword matching: 'Solubility in two different solvents' = 'Differential Extraction'. Chromatography is based on adsorption, distillation on boiling point difference, and sublimation on vapor pressure. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry Some Basic Principles and Techniques

### Core Logic Step 1: Identify the principal functional group. The -CN$-CN$ (nitrile) group has higher priority than the -NH_2$-NH_2$ (amino) group. Step 2: Find the longest carbon chain containing the principal functional group. The chain contains 4 carbon atoms: Butane. Step 3: Number the carbon chain starting from the carbon atom of the nitrile group as C1. overset4mathrmCH_3 - overset3mathrmCH(mathrmNH_2) - overset2mathrmCH_2 - overset1mathrmCN$\overset{4}{\mathrm{CH}_3} - \overset{3}{\mathrm{CH}}(\mathrm{NH}_2) - \overset{2}{\mathrm{CH}_2} - \overset{1}{\mathrm{CN}}$ Step 4: The substituent -NH_2$-NH_2$ is at position 3. Prefix is '3-Amino'. Step 5: Combine to form the IUPAC name: 3-Aminobutanenitrile. ### Pattern Recognition Prioritize functional groups: Nitrile >$>$ Amino. Always count the carbon of the nitrile group in the parent chain. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Organic Chemistry Some Basic Principles and Techniques