The stabilization of anions by sulfides, sulfoxides, and sulfones is a theme that runs right through this chapter. Sulfur has six electrons in its outer shell. As a sulfide, therefore, the sulfur atom carries two lone pairs. In a sulfoxide, one of these lone pairs is used in a bond to an oxygen atom—sulfoxides can be represented in at least two alternative but equivalent ways. The sulfur atom in a sulfone uses both of its lone pairs in bonding to oxygen, and is usually represented with two S=O double bonds.

Treatment of any of these compounds with strong base produces an anion on what was the methyl group. How does the sulfur stabilize the anion? This question has been the subject of many debates and we have not got space to go into the details of all of them. There are at least two factors involved, and the fi rst is evident from this chart of pKa values for protons next to sulfone, sulfoxide, and sulfide functional groups.

Clearly, the oxygen atoms are important—the best anion stabilizer is the sulfone, followed by the sulfoxide and then the sulfide. You could compare deprotonation of a sulfone with deprotonation of a ketone to give an enolate. Enolates have a planar carbon atom and the anion is mainly on the oxygen atom. Sulfone-stabilized carbanions have two oxygen atoms and the anionic carbon atom is probably planar, with the negative charge in a p orbital aligned midway between the S=O bonds.

Yet the attached oxygen atoms cannot be the sole reason for the stability of anions next to sulfur because even the sulfide functional group also acidifies an adjacent proton quite significantly. There is some controversy over exactly why this should be, but the usual explanation is that polarization of the sulfur’s 3s and 3p electrons (which are more diffuse, and therefore more polarizable, than the 2s and 2p electrons of oxygen) contributes to the stabilization.

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عباس.. طفل فقد والده فوجد في خدمة زائري عاشوراء وطنًا آمنًا

شعبة الخطابة النسوية تواصل إقامة مجالس العزاء في شهر المحرم الحرام

لليوم الخامس.. العتبة العباسية المقدسة تقيم مجلس عزاء في صحن مرقد أبي الفضل العباس (عليه السلام)

قسم الشؤون الفكرية يقيم مجلس عزاء حسيني في العاصمة التنزانية دار السلام

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الآخبار الصحية

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دراسة تكشف علاقة خطيرة بين عمر الأم وصحة مولودها

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الآخبار التكنلوجية

هل هاتفك مراقب؟.. 5 علامات خطيرة تكشف التجسس عليك

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المزيد

مواضيع ذات صلة

Sulfur is a very versatile element

Symmetry in intramolecular crossed Claisen condensations

Intramolecular crossed Claisen ester condensations

Crossed Claisen ester condensations between two different esters

Directed C-acylation of esters

Claisen condensations between ketones and esters

Reactive esters that cannot enolize

The Claisen ester condensation and other self-condensations

Problems with acylation at carbon

Cross-condensations

The aldol reaction

Nitroalkanes are superb nucleophiles for conjugate addition