Hydrogen is small enough to move across a conjugated framework through a compact cyclic transition-state arrangement. In a [1,5]-hydrogen shift, an H bonded at one end of a…

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[2+2] Cycloadditions: Thermal Forbiddenness and Ketenes

Joining two C=C bonds into a cyclobutane seems like a simple counterpart to the Diels–Alder reaction. Yet two ordinary alkenes usually do not form a cyclobutane by a concerted…

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1,3-Dicarbonyl Compounds and Stabilised Enolates

A 1,3-dicarbonyl compound contains two carbonyl groups separated by one carbon. If that central carbon bears hydrogen, it is often far more acidic than an alpha carbon next to…

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1,3-Dipolar Cycloadditions

Four- and six-membered rings do not exhaust cycloaddition chemistry. A three-atom 1,3-dipole can combine with an alkene or alkyne two-atom component to make a five-membered ring.…

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1,5-Dicarbonyls and the Michael Reaction

A 1,5-dicarbonyl pattern often points backward to a Michael addition. One carbonyl-containing fragment acted as a nucleophilic donor, and an α,β-unsaturated carbonyl acted as an…

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118 Element Profiles

Browse all 118 elements in the Kalviyogi ChemLab periodic table, with Tamil and English learning content and element profiles.

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¹³C Chemical Shifts

Knowing how many carbon environments a molecule has is only half of ¹³C NMR. The other half is where each line appears. Carbon chemical shifts cover a range of more than 200 ppm…

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