四氟化硫是一種選擇性有機(jī)氟化劑，它的分子結(jié)構(gòu)上S原子以sp3d雜化軌道形成σ鍵，分子形狀為變形四面體形，在常溫常壓下為無色帶有類似二氧化硫氣體的強(qiáng)烈刺激臭氣味的氣體，有毒，在空氣中不燃燒，不爆炸；在600℃時(shí)仍很穩(wěn)定。在空氣中強(qiáng)烈水解冒出白煙。遇到有水分的環(huán)境會(huì)引起類似氫氟酸的腐蝕。完全水解變成二氧化硫和氫氟酸，部分水解時(shí)，生成有毒的亞硫酰氟，但能被強(qiáng)堿溶液全部吸收變成無毒無害的鹽類；能溶于苯。
SF4是氟代能力很強(qiáng)的一種試劑，通常和HF一起使用。除了能把羥基化合物轉(zhuǎn)化為單氟代化合物，醛和酮轉(zhuǎn)化為二氟代化合物之外，還能把羧基轉(zhuǎn)化為三氟甲基，是合成三氟甲基化合物的一個(gè)重要方法，特別是芳香類三氟甲基化合物。
SF4在氟化學(xué)的發(fā)展史上是很重要的一種氟代試劑，隨著DAST等新型氟代試劑的發(fā)展，SF4在氟化學(xué)中的應(yīng)用逐漸減少，對(duì)羥基化合物和醛酮的氟代反應(yīng)基本已被DAST等試劑取代。
SF4最重要的應(yīng)用就是從羧酸合成三氟甲基化合物。脂肪族羧酸為底物反應(yīng)收率不高，生成的副產(chǎn)物是醚【Dmowski,W; Kolinski, R, A. Pol. J. Chem. 1974, 48, 1697】。
芳香族羧酸底物的產(chǎn)率還可以，不過反應(yīng)需要加入20－30當(dāng)量的HF，反應(yīng)操作不方便?！?em>Zh. Org. Khim. 1974, 10, 886】
反應(yīng)示例
Twenty-six grams (0.20 mole) of heptanoic acid is placed in a 145-mL pressure vessel linedwith Hastelloy-C. The air in thevessel is displaced with nitrogen, and the head ofthe vessel is secured in place. Thevessel is cooled in a bath of acetone and solid carbon dioxide, and the nitrogenin the vessel is evacuated with a vacuum pump to apressure of 0.5–1.0 mm. Sixty-five grams (95% pure, 0.57 mole) of sulfur tetrafluoride is transferred to the cold vessel. This is conveniently done by connecting a cylinder containing 65 g of sulfur tetrafluoride to the pressure vessel by a lengthof copper tubing having a 1/16-in. bore and 1/8-in.outside diameter.
The pressure vessel is heated with agitation at 100° for 4 hoursand at 130° for 6 hours. The vessel is allowed to cool to room temperature andthe volatile by-products [ Caution!Toxic!] are vented. The crude, fuming, liquid product is pouredinto a stirred suspension of 10 g. of finely divided sodium fluoride in 60 mL of pentane, the mixture is filtered, and the filtrate isfractionated through a 6-in. Vigreux column. 1,1,1-Trifluoroheptane is collected at 100–101°/760 mm., nD251.3449. The yield is 21.7–24.6 g. (70–80%).
【Hasek, W, R. OrganicSynthese. Coll. Vol. 5, 1082.】
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