(E)-2,4-ジクロロ-(1-2H)-1-ペンテン

外観

灰黒色の小塊

溶解性

水に不溶。アルコ-ルに不溶。高温の水蒸気では水素を発生してホウ酸を生じる。硝酸により容易に酸化され, ホウ酸, 酸化窒素などを生じる。融解アルカリとはホウ酸塩を与える。

主な性質

1. 単体ボロンは黒灰色を帯びた耐火性の非金属固体である
2. 単体ボロンはダイヤモンドに次いで硬く、電気的には金属と非金属の間の半導体的な性質を持つ
3. 化学的には硫酸や濃硝酸にわずかに反応する。700℃に加熱すると酸素中で燃え、１５００℃で窒素ガスに反応する
4. ボロンを含む化合物は多様に存在する。チタン、ジルコニウム、クロムとの金属化合物は耐熱塗装剤として使われる。ボロンを混ぜたガラスは耐熱硬質ガラスとして多用
5. 水素との化合物は一般に高い反応性を示す（還元剤、水素発生源として利用）

解説

ホウ素，元素記号B，原子番号5，原子量 10.811。周期表 13族に属する。主要鉱石はホウ砂，カーン石，コールマン石などがある。火成岩中に広く分布し，地殻の平均含有量 10ppm，海水中の平均濃度 4.6 mg/l 。単体は黒灰色，金属光沢のある半金属固体で，比重 2.33 (無定形ホウ素は 1.73) ，融点 2000～2500℃。化学的性質はケイ素に類似し，不活発。塩酸，フッ化水素酸におかされないが，アルカリ溶融により分解される。還元性があり，銅の脱酸剤ともなる。単体としての用途はあまりないが，化合物はガラスなどの原料として重要である。

用途

高融点金属ほう化物の原料、金属精錬時の脱酸素剤、半導体材料の原料。

用途

電子材料、合金材料、触媒。

用途

最大の用途は，ガラス繊維用でFRPなどの補強材，電気絶縁体，断熱材などとして使われる．ホウケイ酸ガラス(硬質ガラス)製造用がこれにつぎ，そのほかうわぐすり，医薬品(目薬，消毒薬)などに用いられる．フェロボロンはホウ素を10～20％ 程度含み，焼入れ硬化性，溶接性向上用として特殊鋼に添加される．最強の永久磁石Nd-Fe-B磁石製造用にも使われる．グラファイト型窒化ホウ素は高温用電気絶縁材や，潤滑剤として，ダイヤモンド型窒化ホウ素は切削工具に使われる．仕事関数の低い六ホウ化ランタンLaB6は，熱電子放射用に電子銃に利用，炭化ボロンB4Cは研磨剤，原子炉用制御材．高純度ホウ素は半導体用のドーパントとして重要である．LiB4O7は，携帯電話では必要な信号を取り出すためのフィルタ用弾性表面波素子として使われている．

主な用途

1. ガラス長繊維（ＦＲＰ船、プリント基盤）
2. ガラスの短繊維（建築物、冷蔵庫）
3. ホウケイ酸ガラス（自動車、液晶ディスプレー）
4. うわぐすり（陶磁器）
5. フェロボロン（低合金鋼、磁石等）
6. 医療（目薬、消毒薬等）
7. 防虫剤（ゴキブリ防虫剤等）
8. 金属表面処理剤（溶融塩浴等）
9. γ線遮断ブロック（原子炉の遮断壁）

説明

Boron was discovered by Sir Humphry Davy and J.L. Gay-Lussac in 1808. It is a trivalent non-metallic element that occurs abundantly in the evaporite ores borax and ulexite. Boron is never found as a free element on Earth. Boron appears as charcoal-grey pieces or black powder or as crystalline; is a very hard, black material with a high melting point; and exists in many polymorphs.

Boron has several forms, and the most common one is amorphous boron, a dark powder, non-reactive to oxygen, water, acids, and alkalis. It reacts with metals to form borides. Boron is an essential plant micronutrient. Sodium borate is used in biochemical and chemical laboratories to make buffers. Boric acid is produced mainly from borate minerals by the reaction with sulphuric acid. Boric acid is an important compound used in textile products. The most economically important compound of boron is sodium tetraborate decahydrate or borax, used for insulating fibreglass and sodium perborate bleach. Compounds of boron are used in organic synthesis, in the manufacture of a particular type of glasses, and as wood preservatives. Boron filaments are used for advanced aerospace structures, due to their high strength and light weight.

化学的特性

Boron is a yellow or brownish-black powder and may be either crystalline or amorphous. It does not occur free in nature and is found in the minerals borax, colemanite, boronatrocalcite, and boracite. It is insoluble in water but soluble in nitric and sulfuric acids. It is insoluble in cold water, hot water, diethyl ether, and alcohol. If finely divided, it is soluble in most molten metals such as copper, iron, magnesium, aluminum, and calcium. Borates are relatively soluble in water.

分布

天然に広く分布しており，おもにアルカリ金属またはアルカリ土類金属のホウ酸塩の形で存在している．地殻中の存在度は10 ppm．資源として利用される鉱物はおもにコールマン石(コレマナイト)Ca2B6O11･5H2O．埋蔵量は1位トルコ(35％)，ついでアメリカ(24％)，ほかロシア，中国など．わが国にはホウ素資源がないため，原料鉱石および中間製品ホウ砂，ホウ酸は全量輸入に頼り，鉱石は8割がトルコから，ホウ砂・ホウ酸は合わせて7割がアメリカからである．

物理的性質

Boron has only three electrons in its outer shell, which makes it more metal than nonmetal.Nonmetals have four or more electrons in their valence shell. Even so, boron is somewhatrelated to metalloids and also to nonmetals in period 2.
It is never found in its free, pure form in nature. Although less reactive than the metalswith fewer electrons in their outer orbits, boron is usually compounded with oxygen andsodium, along with water, and in this compound, it is referred to as borax. It is also found asa hard, brittle, dark-brown substance with a metallic luster, as an amorphous powder, or asshiny-black crystals.
Its melting point is 2,079°C, its boiling point is 2,550°C, and its density is 2.37 g/cm³.

同位体

There are a total of 13 isotopes of boron, two of which are stable. The stableisotope B-10 provides 19.85% of the element’s abundance as found in the Earth’s crust,and the isotope B-11 provides 80.2% of boron’s abundance on Earth.

名前の由来

It is named after the Arabic word bawraq, which means “white borax.”

天然物の起源

Boron is the 38th most abundant element on Earth. It makes up about 0.001% of theEarth’s crust, or 10 parts per million, which is about the same abundance as lead. It is notfound as a free element in nature but rather in the mineral borax, which is a compound ofhydrated sodium, hydrogen, and water. Borax is found in salty lakes, dry lake-beds, or alkalisoils. Other naturally occurring compounds are either red crystalline or less dense, dark-brownor black powder.
Boron is also found in kernite, colemanite, and ulexite ores, and is mined in many countries,including the western United States.

特性

Boron is a semimetal, sometimes classed as a metallic or metalloid or even as a nonmetal.It resembles carbon more closely than aluminum. Although it is extremely hard in its purified form—almost as hard asdiamonds—it is more brittle than diamonds, thus limiting its usefulness. It is an excellentconductor of electricity at high temperatures, but acts as an insulator at lower temperatures.

使用

Boron has found many uses and has become an important industrial chemical. Boron is used as an alloy metal, and when combined with other metals, it imparts exceptional strength to those metals at high temperatures. It is an excellent neutron absorber used to capture neutrons in nuclear reactors to prevent a runaway fission reaction. As the boron rods are lowered into the reactor, they control the rate of fission by absorbing excess neutrons. Boron is also used as an oxygen absorber in the production of copper and other metals, Boron finds uses in the cosmetics industry (talc powder), in soaps and adhesives, and as an environmentally safe insecticide. A small amount of boron is added as a dope to silicon transistor chips to facilitate or impede the flow of current over the chip. Boron has just three valence electrons; silicon atoms have four. This dearth of one electron in boron s outer shell allows it to act as a positive hole in the silicon chip that can be filled or left vacant, thus acting as a type of switch in transistors. Many of today s electronic devices depend on these types of doped-silicon semiconductors and transistors. Boron is also used to manufacture borosilicate glass and to form enamels that provide a protective coating for steel. It is also used as medication for relief of the symptoms of arthritis. Due to boron s unique structure and chemical properties, there are still more unusual compounds to be explored.

定義

boron: Symbol B. An element ofgroup 13 (formerly IIIB) of the periodictable; a.n. 5; r.a.m. 10.81; r.d.2.34–2.37 (amorphous); m.p. 2300°C;b.p. 2550°C. It forms two allotropes;amorphous boron is a brown powderbut metallic boron is black. Themetallic form is very hard (9.3 onMohs’ scale) and is a poor electrical conductor at room temperature. Atleast three crystalline forms are possible;two are rhombohedral and theother tetragonal. The element isnever found free in nature. It occursas orthoboric acid in volcanic springsin Tuscany, as borates in kernite(Na₂B₄O₇.4H₂O), and as colemanite(Ca₂B₆O₁₁.5H₂O) in California. Samplesusually contain isotopes in theratio of 19.78% boron–10 to 80.22%boron–11. Extraction is achieved byvapour-phase reduction of borontrichloride with hydrogen on electricallyheated filaments. Amorphousboron can be obtained by reducingthe trioxide with magnesium powder.Boron when heated reacts withoxygen, halogens, oxidizing acids,and hot alkalis. It is used in semiconductorsand in filaments for specializedaerospace applications.Amorphous boron is used in flares,giving a green coloration. The isotopeboron–10 is used in nuclear reactorcontrol rods and shields. Theelement was discovered in 1808 bySir Humphry Davy and by J. L. Gay-Lussac and L. J. Thenard.

製造方法

Boron may be prepared by several methods, such as chemical reduction of boron compounds, electrolytic reduction in nonaqueous phase, or by thermal decomposition. Many boron compounds including boron oxides, borates, boron halides, borohydrides, and fluoroborates can be reduced to boron by a reactive metal or hydrogen at high temperatures:
B2O₃ + 3Ca → 2B + 3CaO
The metal is obtained as a black amorphous product.
2BCl₃ + 3H₂ → 2B + 6HCl
High purity grade boron may be prepared by such hydrogen reduction at high temperatures using a hot filament.
Electrolytic reduction and thermal decomposition have not yet been applied in large scale commercial methods. Electrolysis of alkali or alkaline earth borates produces boron in low purity. Electrolytic reduction of fused melts of boron trioxide or potassium tetrafluroborate in potassium chloride yield boron in high purity. Also, boron tribromide or boron hydrides may be thermally dissociated by heating at elevated temperatures.
Impurities from boron may be removed by successive recrystallization or volatilization at high temperatures. Removal of certain impurities such as oxygen, nitrogen, hydrogen or carbon from boron are more difficult and involve more complex steps.

調製方法

Until the late 1990s elemental boron had not found widespread use in industry, where cost of production was a major obstacle. Now, there is increasing use as new applications for the element are developed in material composites and use in nanotechnology.

发现

天然には遊離の状態では存在しない．安定同位体は質量数10(19.9(7)％)，11(80.1(7)％)で，ほかに質量数6～9，12～19の放射性同位体がある．数千年前からホウ酸，あるいはホウ砂の形で知られていた．1808年6月，10日足らずの差で，まずフランスのL-J. Gay-Lussac(ゲイ-リュサック)とL-J. Thénard，ついでイギリスのH. Davy(デイビー)がホウ酸から元素の分離成功を発表した．ホウ砂borax(英・フランス語とも)から，フランス側はbore，イギリス側はboraciumを提案，元素名は英語ではこの元素の周期表上の位置が炭素(carbon)に近いことからboronとなり，フランス語はそのままbore，ドイツ語ではBorとなった．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で，勃母(ボリュウム)，ボラキス・ストフとしている．ホウ酸またはホウ砂などのホウ酸塩の形で昔から知られていた．

製法

(1)三酸化二ホウ素を金属マグネシウムで還元する方法で，1895年にH. Moissanが開発し，今日も使用されている．量産に適しているが，純度の高いものは得られない．99％ 以上の純度のものは，

(2)水素気流中で三塩化ホウ素を，タングステンフィラメント上で，約1000 ℃ で熱分解する，

(3)ジボランをヘリウムと混合して，700 ℃ のシリカ管中で分解する，

(4)ホウフッ化カリウムと三酸化二ホウ素を融解した塩化カリウムに溶かして約1000 ℃ で電解する

危険性

Powdered or fine dust of elemental boron is explosive in air and toxic if inhaled. Several ofthe compounds of boron are very toxic if ingested or if they come in contact with the skin. Thisis particularly true of the boron compounds used for strong insecticides and herbicides.

健康ハザード

Boron has been studied extensively for its nutritional importance in animals and humans. There is a growing body of evidence that boron may be an essential element in animals and humans. Many nutritionists believe that people would benefi t from more boron and many popular multivitamins, such as centrum, in the diet. The adverse health effects of boron on humans is limited. However, ingestion/inhalation causes irritation to the mucous membrane and boron poisoning. Short-term exposures to boron in work areas are known to cause irritation of the eye, the upper respiratory tract, and the naso-pharynx, but the irritation disappears with the stoppage of further exposure. Ingestion of large amounts of boron (about 30 g of boric acid)over short periods of time is known to affect the stomach, intestines, liver, kidney, and brain and can eventually lead to death in exposed people.

工業用途

Boron (symbol B) is a metallic element closelyresembling silicon. Boron has a specific gravityof 2.31, a melting point of about 2200°C, anda Knoop hardness of 2700 to 3200, equal to aMohs hardness of about 9.3. At 600°C, boronignites and burns with a brilliant green flame.Minute quantities of boron are used in steelsfor case hardening by the nitriding process toform a boron nitride, and in other steels toincrease hardenability, or depth of hardness. Inthese boron steels, as little as 0.003% is beneficial,forming an iron boride, but with largeramounts the steel becomes brittle and susceptibleto hot-short unless it contains titanium orsome other element to stabilize the carbon . Incast iron, boron inhibits graphitization and alsoserves as a deoxidizer. It is added to iron andsteel in the form of ferroboron.
Boron compounds are employed for fluxesand deoxidizing agents in melting metals, andfor making special glasses. Boron, like siliconand carbon, has an immense capacity for formingcompounds, although it has a differentvalence. The boron atom appears to have a lenticularshape, and two boron atoms can make astrong electromagnetic bond, with the boronacting like carbon but with a double ring.

職業ばく露

Boron is used in metallurgy as a degasifying agent and is alloyed with aluminum, iron, and steel to increase hardness. It is also a neutron absorber in nuclear reactors. Boron is frequently encountered in a variety of chemical formulations including boric acid, various borate salts, borax, and boron soil supplements.

輸送方法

Boron powder or dust: UN3178 Flammable solid, inorganic, Hazard Class: 4.1; Labels: 4.1—Flammable solid.

Structure and conformation

The space lattice of Boron belongs to the tetragonal system with lattice constants a=0.873 nm, c=1.013 nm (c=0.503 nm is also reported). The rhombohedron system is also formed. The rhombohedron is stable near the melting point.
Energy gap: Eg=1.0–1.5 eV
Activation energy : 1.39±0.05 eV
Electron mobility: μe=0.9 cm2 /V s (300 K, 1.8×10¹⁶ cm^-3 )

不和合性

Boron dust may form explosive mixture in air. Contact with strong oxidizers may cause explosions. Violent reaction (possible explosion) with concentrated nitric acid, hydrogen iodide; silver fluoride. Boron is incompatible with ammonia, bromine tetrafluoride, cesium carbide, chlorine, fluorine, interhalogens, iodic acid, lead dioxide, nitric acid, nitrosyl fluoride, nitrous oxide, potassium nitrite, rubidium carbide. Reacts exothermically with metals at high temperature above 900° C.

廃棄物の処理

Dispose of contents and container to an approved waste disposal plant. All federal, state, and local environmental regulations must be observed.

予防処置

Elemental boron is non-toxic and common boron compounds, such as borates and boric acid, have low toxicity (approximately similar to table salt with the lethal dose being 2–3 g/kg) and do not require special precautions while handling. Some of the more exotic boron hydrogen compounds, however, are toxic as well as highly flammable and do require special care when handling