HYDRAZINE Here's the inside story
of its intriguing molecular anatomy. One potent N-N bond, two free electron pairs and four substitutable hydrogen atoms. These are the unique characteristics of the hydrazine molecule. The incredible range of things you can accomplish by manipulating thebond, reacting the electrons and sub stituting the hydrogens is what makes hydrazine's characteristics so intriguing to research chemists. Perhaps an in sight into how these characteristics re late to specific properties will turn your thinking in a profitable new direction. A word about its bond Hydrazine is a chemical rarity: The same molecule can act as either a re ducing agent or an oxidizing agent. The N-N bond is the reason. The N-N bond puts nitrogen in the -2 valence state. Nitrogen's natural bent, however, is to the 0 state (ΝΞΝ], To get there, hydrazine must act as a reducing agent. And since the formation of ΝΞΝ gives off nearly six times as much energy as the N-N bond, the reducing action is plenty powerful. No wonder hy drazine is popular in such uses as corrosion protection in boilers, the hydrogénation of unsaturated bonds and the scavenging of halogens. A new and growing scavenging use is to remove troublesome chromâtes from effluents. Hydrazine reduces the valence of the chromium in the chromate ion. The chromate then forms insoluble chromium hydroxide, which is easily precipitated out. The hydrazine is oxidized to N2 and H 2 0, adding no harmful chemicals to the system. CrO;-^Cr--^Cr(OH)3 + Hydrazine will act as an oxidizer if you split the N-N bond. A good example is in the hydrogénation of certain hydrazine derivatives to make amines, where more classical methods would give mixtures that are difficult to separate. In theory, hydrazine should be a good oxidizing agent. In practice, it's seldom used for oxidation, mostly because the reactions are usually too
slow. Find the right catalyst, though, and you could go places fast. Incidentally, the strong drive of the N-N bond toward N2 is what makes hydrazine especially effective in applications such as pesticides, where vigorous biological activity is desirable, but persistence in the environment isn't. Much ado about negativity Each nitrogen atom has a pair of free electrons, occupying the vacant tetrahedral position. These electron pairs will react with anything that will accept them, making hydrazine a Lewis base. [Hydrazine is also an Arrhenius base, which is important because many hydrazine reactions take place in water.)
If the free electrons react with protons, hydrazine salts are formed. Sometimes you'll want to form salts for more convenient handling. Because of the electron pairs, hydrazine is a nucleophile. Either N-site can react, and the reactions at each site can be identical or completely different. So you can form a whole series of new compounds: Azines and hydrazones from ketones and aldehydes. Hydrazides from acyl compounds. Hydroxyalkyl hydrazines from epoxides. Pyrazolones from ketoesters. Substituted pyrazolesfrom diketones. And pyrazolinesfrom keto-olefins. CIRCLE 44 ON READER SERVICE CARD
If two functional groups are in separate molecules, you can also use hydrazine's nucleophilicity for chain extension or cross-linking. Polyisocyanates are an example: Ο 0 =C=N ^ N =C - ^ O O N - w ^ Ο Ο NH-C-NHNH-C-NH^N = C = 0 A new kind of 4-H club You can substitute various groups for any or all of hydrazine's four hy drogen atoms. What's more, you can substitute without disturbing the free electron pairs, avoiding the inadvertent formation of salts And despite all this commo tion, you keepthe basic N-N linkage intact and ready for action. The plant growth regulator Alar* is an example. Ο HOOC-CH2CH2Q CH3 N-N H CH3 Now that you know more about how the hydrazine molecule works, maybe you've already got a glim mer of how to make it work for you. If so, we have more to offer you. There's our hydrazine chem istry brochure. It tells you briefly about some of the ways you can react this versatile molecule. There's our unique hydrazine data bank that can search more than 20,000 hydrazine technical refer ences for you. It leads you right to the information that's likely to help you most, without burdening you with extraneous material. And there are pro duct samples to think with. And once you get started, we'll keep you going. We've tripled our capa city, to 21 million lbs. Let us help you put it all together. Whatever you need, just ask for it by writing on your company letterhead to: Hydrazine Marketing Manager, Olin Chemicals, Dept. 2F-137HR, 120 Long Ridge Road, Stamford, CT 06904. trademark of Uniroyal, Inc.
Olin
CHEMICALS October 22, 1984 C&EN
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