Which compound in each of the following pairs is more basic? (a) CH3 CH2 NH2 or CH3 CH2 CONH2 (b

step 1 Which compound in each pair is more basic? Bacicity of amines are due to this long pair on nitro

Which compound in each of the following pairs is more basic?...

Which compound in each of the following pairs is more basic?
(a) $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}$ or $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CONH}_{2}$
(b) $\mathrm{NaOH}$ or $\mathrm{CH}_{3} \mathrm{NH}_{2}$
(c) $\mathrm{CH}_{3} \mathrm{NHCH}_{3}$ or pyridine

Key Concepts

Basicity

Basicity refers to the ability of a molecule or ion to accept a proton (H+). It is determined by the availability and electron density of a lone pair on an atom, which can stabilize the positive charge in the resulting conjugate acid. Understanding basicity is essential when comparing compounds because the more available the lone pair, the stronger the base.

Electron Donating and Withdrawing Effects

Electron donating groups (EDGs) increase electron density on the basic atom, thereby enhancing basicity by making the lone pair more available for protonation. Conversely, electron withdrawing groups (EWGs) pull electron density away, decreasing the availability of the lone pair and thus reducing the compound's basicity. This effect is particularly important in differentiating between similar functional groups with different substituents.

Resonance Effects

Resonance effects occur when the lone pair on the basic atom is delocalized over a conjugated system. This delocalization lowers the electron density on the atom, making it less available for bonding with a proton. In many cases, functional groups that participate in resonance stabilization display diminished basicity compared to those where the lone pair remains localized.

Hybridization Effects

The hybridization of the atom bearing the lone pair can significantly influence basicity. Atoms with sp3 hybridization typically have lone pairs that are held in orbitals with more p-character and less effective nuclear charge, making them more available for protonation compared to lone pairs in sp2 hybridized atoms, which are generally held more tightly and are less accessible.

Ionic Versus Covalent Bases

Ionic bases, which often come in the form of metal hydroxides, dissociate completely in aqueous solution, releasing high concentrations of basic ions that can readily accept protons. In contrast, covalent or molecular bases, such as amines, do not dissociate in the same way and are typically weaker bases. This distinction is important when comparing the relative basic strengths of compounds in solution.

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