每周分子Molecule of the Week
Molecule of the Week: Phosphine
每周分子：磷烷
磷烷是最简单的氢化磷，是一种无色的有毒气体。有些人认为它闻起来像腐烂的鱼；让人想起大蒜的味道。在任何情况下，纯磷烷实际上是没有气味的；杂质二磷烷(P2H4)是其恶臭的根源。
磷烷是由含磷有机物的厌氧分解自然形成的。磷烷最早的制备是在18世纪末由Antoine Lavoisi的学生Philippe Gengembre完成的。
磷烷在工业上是由白磷与碱金属氢氧化物水解或通过水溶液中的酸催化歧化反应而成。工业产品通常以液化气体的形式装运。
虽然磷烷的分子结构类似于氨，但其磷原子的3d轨道与氢原子相互作用，降低了其氢键的能力。因此，氨极易溶于水，而磷烷的水溶性却很低。
危险信息表显示，在地球上，磷烷有多种危害。但最近的发现表明，磷烷在外层空间的存在可能对生命起源起了关键作用。
夏威夷大学马诺亚分校（檀香山）的Ralf I. Kaiser及其同事们在接近绝对零度的温度下，将磷烷、二氧化碳、水和氧气结合在一起，模拟在太空中发现的冰。然后，他们用高能电子（太空中发现的电子）轰击冰来生成几种磷氧酸（包括一些在DNA、ATP和其他重要生物分子中存在的、相同磷氧化态的酸）。
今年美国化学周的主题是“地球外的化学”。以庆祝人类认识到外太空的磷烷对生命的潜在贡献。
磷烷信息速览
| CAS 登记号 | 7803-51-2 |
| 分子式 | H3P |
| 摩尔质量 | 34.00 g/mol |
| 外观 | 无色气体 |
| 沸点 | –87.7 ºC |
| 水溶性 | ≈300 mg/L |
磷烷危害信息
| GHS 分类*: 易燃气体，分类1 | |
| H220—极易燃气体 | |
| GHS 分类: 压力气体，压缩气体 | |
| H280—压力下含有气体；加热会爆炸 | |
| GHS 分类：皮肤腐蚀，分类1B | |
| H314—致严重的皮肤烧伤和眼损伤 | |
| GHS 分类：严重的眼损害，分类1 | |
| H318—致严重的眼损害 | |
| GHS 分类：急性毒性，吸入，分类1 | |
| H330—吸入致死 | |
| GHS 分类：危害水生环境，急性危害，分类1 | |
| H400—对水生环境剧毒 |
【关于每周分子 】
自2001年以来，“每周分子”已成为广受欢迎的栏目。多数分子由读者推荐。每个结构都经由科学家审查，并以3-D和平面图像的形式显示，同时附有该分子简介。可以通过美国化学文摘社（CAS）提供的SciFinder中的CAS REGISTRY获取每周分子的更多信息。CAS REGISTRY中的每条物质信息都展示了物质的CAS登记号、索引名、通用名、商品名、书目信息等其他更多信息。发送邮件至motw@acs.org推荐您感兴趣的分子。
Phosphine, the simplest phosphorus hydride, is a colorless and extremely toxic gas. Some people think it smells like rotting fish; it reminds others of the odor of garlic. In any case, pure phosphine is actually odorless; an impurity, diphosphane (P2H4), is responsible for its foul scent.
Phosphine is formed naturally via the anaerobic decay of phosphorus-containing organic matter. The earliest reported preparation was made by Antoine Lavoisier’s student Philippe Gengembre in the late 18th century.
Phosphine is made industrially from white phosphorus by hydrolysis with an alkali metal hydroxide or an aqueous acid–catalyzed disproportionation reaction. The industrial product is normally shipped as liquefied gas.
Although phosphine’s molecular structure is analogous to that of ammonia, the 3d orbital of its phosphorus atom interacts with its hydrogen atoms to reduce its ability to hydrogen bond. Thus, whereas ammonia is completely miscible in water, the aqueous solubility of phosphine is very low.
The hazard information box shows that phosphine is dangerous in several ways on Earth. But recent findings indicate that its presence in outer space may have had a key role in the beginnings of life.
Ralf I. Kaiser at the University of Hawaii at Manoa (Honolulu) and his colleagues simulated ices found in space by combining phosphine, carbon dioxide, water, and oxygen at near–absolute zero temperatures. They then bombarded the ices with high-energy electrons (typical of those found in space) to produce several phosphorus oxyacids, including some with the same phosphorus oxidation state that exists in DNA, ATP, and other important biomolecules.
The theme of this year’s National Chemistry Week is “Chemistry Is Out of This World”. Celebrate it by recognizing extraterrestrial phosphine’s potential contribution to life.
Phosphine fast facts
| CAS Reg. No. | 7803-51-2 |
| Empirical formula | H3P |
| Molar mass | 34.00 g/mol |
| Appearance | Colorless gas |
| Boiling point | –87.7 ºC |
| Water solubility | ≈300 mg/L |
Phosphine hazard information
| GHS classification*: flammable gases, category 1 | |
| H220—Extremely flammable gas | |
| GHS classification: gases under pressure, compressed gas | |
| H280—Contains gas under pressure; may explode if heated | |
| GHS classification: skin corrosion, category 1B | |
| H314—Causes severe skin burns and eye damage | |
| GHS classification: serious eye damage, category 1 | |
| H318—Causes serious eye damage | |
| GHS classification: acute toxicity, inhalation, category 1 | |
| H330—Fatal if inhaled | |
| GHS classification: hazardous to the aquatic environment, acute hazard, category 1 | |
| H400—Very toxic to aquatic life |
*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.
About Molecule of the Week
MOTW has been a popular feature on ACS website since 2001. Many molecules are suggested by our website visitors. Every structure is reviewed by a scientist and displayed in 3-D and flat images with a brief description. Each week’s molecule also links to a sample record from the CAS REGISTRY, which is searched using SciFinder. Each record displays the registry number, index name and synonyms, bibliographic information, and more. Send us a molecule suggestion at motw@acs.org.
Copyright © 2018 American Chemical Society.
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