What went wrong when the king rode under the arch?

It was too low and knocked off his crown

How does the chain of blame unfold in the poem?

Each accused person blames another, ending with the king's own changes

Who disproved the vital-force theory and how?

Friedrich Wöhler, by synthesising urea from ammonium cyanate, an inorganic salt, in 1828.

Why is an sp-hybridised carbon the most electronegative?

It has the greatest s-character (50 percent), which holds the bonding electrons closer to the nucleus.

Why is rotation about a carbon-carbon double bond restricted?

The pi bond requires sidewise overlap of parallel p-orbitals, which is lost on rotation.

By what unit do successive members of a homologous series differ?

By a CH\(_2\) group, corresponding to a difference of 14 in molar mass.

Name the four types of structural isomerism.

Chain, position, functional-group and metamerism.

Distinguish homolytic from heterolytic bond fission.

In homolysis each atom keeps one electron, forming free radicals; in heterolysis the pair stays with one atom, forming a carbocation and a carbanion.

What is the order of carbocation stability?

Tertiary > secondary > primary > methyl, owing to inductive and hyperconjugative electron release.

Distinguish a nucleophile from an electrophile.

A nucleophile is electron-rich and donates an electron pair, while an electrophile is electron-deficient and accepts one.

Name a test for nitrogen, sulphur and halogens in organic compounds.

Lassaigne's sodium-fusion test, which converts these elements into ionic forms detectable in solution.

What technique purifies a volatile solid that sublimes?

Sublimation, in which the solid is converted directly to vapour and re-deposited as a pure solid.

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Chapter 2: Organic Chemistry – Some Basic Principles and Techniques — Class 11 Chemistry

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Chapter 2: Organic Chemistry – Some Basic Principles and Techniques

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The vital-force theory was disproved when Wöhler synthesised:

Summary

This foundational unit sets out the principles needed to study carbon compounds, beginning with the historical collapse of the vital-force theory after Wöhler synthesised urea in the laboratory. Carbon's tetravalence and its unique ability to catenate, explained through sp\(^3\), sp\(^2\) and sp hybridisation, govern the tetrahedral, planar and linear shapes of organic molecules and the features of pi bonds. Structures are represented by complete, condensed and bond-line formulae, by three-dimensional wedge-and-dash notation and by molecular models. Organic compounds are classified as acyclic (aliphatic), alicyclic, aromatic and heterocyclic, and are grouped by functional group into homologous series whose successive members differ by a CH\(_2\) unit. The IUPAC system names a compound from its parent chain, principal functional group, substituent prefixes and lowest locants. Isomerism is divided into structural (chain, position, functional and metamerism) and stereoisomerism (geometrical and optical). The fundamentals of reaction mechanism cover the homolytic and heterolytic fission of covalent bonds, giving free radicals, carbocations and carbanions; the distinction between nucleophiles and electrophiles; the curved-arrow notation for electron movement; and the electron-displacement effects of induction, resonance, the electromeric effect and hyperconjugation. The unit also introduces the main types of organic reactions and the laboratory techniques of purification (crystallisation, distillation, chromatography) and qualitative and quantitative elemental analysis.

Vital-force theory and tetravalence of carbonShapes of organic compounds and hybridisationStructural representation of moleculesClassification and functional groupsIUPAC nomenclatureStructural and stereo isomerismBond fission, nucleophiles and electrophilesElectron-displacement effectsPurification and elemental analysis

Key terms

Catenation

The ability of carbon to bond to other carbon atoms, forming long chains and rings.

Functional group

An atom or group of atoms in a molecule that determines its characteristic chemical properties, such as \(-OH\) or \(-COOH\).

Homologous series

A family of compounds with the same functional group and general formula, successive members differing by a CH\(_2\) unit.

Carbocation

A positively charged carbon species with only six valence electrons; it is planar and sp\(^2\) hybridised, stability increasing from primary to tertiary.

Nucleophile

An electron-rich, nucleus-seeking reagent that supplies an electron pair to a reactive site.

Inductive effect

The permanent partial displacement of sigma-bond electrons along a chain due to electronegativity differences.

Important questions

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Catenation

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The ability of carbon to bond to other carbon atoms, forming long chains and rings.

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Practice quiz · Organic Chemistry – Some Basic Principles and Techniques

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