chemistry

Symmetrical dimethylhydrazine

Symmetrical dimethylhydrazine is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Symmetrical dimethylhydrazine rather than just read about it. In short: Symmetrical dimethylhydrazine (SDMH), or 1,2-dimethylhydrazine, is the organic compound with the formula (CH3NH)2. It is one of the two isomers of dimethylhydrazine.

Key takeaways

Symmetrical dimethylhydrazine belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Symmetrical dimethylhydrazine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Symmetrical dimethylhydrazine from memory before moving on to harder problems.

Reference excerpt

Symmetrical dimethylhydrazine (SDMH), or 1,2-dimethylhydrazine, is the organic compound with the formula (CH3NH)2. It is one of the two isomers of dimethylhydrazine. Both isomers are colourless liquids at room temperature, with properties like those of methylamines. Symmetrical dimethylhydrazine is a potent carcinogen that acts as a DNA methylating agent. The compound has no commercial value, in contrast to its isomer unsymmetrical dimethylhydrazine(1,1-dimethylhydrazine, UDMH), which is used as a rocket fuel. SDMH is more toxic than unsymmetrical dimethylhydrazine and is often considered an unwanted impurity in UDMH. It is used to induce colon tumors in experimental animals, particularly mice and feline cell samples.

Synthesis The synthesis of symmetrical dimethylhydrazine is a two-step reaction. First N,N′-bis(ethoxycarbonyl)hydrazide is prepared by elimination of HCl from ethyl chloroformate (2 eq, R1) and hydrazine (1 eq, R1) in the presence of NaOH (2 eq, R1). Then the N,N′-bis(ethoxycarbonyl)hydrazide (1 eq, R2) is reduced by lithium aluminum hydride (6 eq, R2) to form symmetrical dimethylhydrazine.

Reactivity The reactive groups of symmetrical dimethyl hydrazine are the NH-groups. Both can accept and donate hydrogen bonds, making it soluble in water. The NH-groups can also act as a nucleophile and as a base.

Biotransformation Symmetrical dimethylhydrazine is first oxidized to azomethane which is then oxidized to azoxymethane. This compound is subsequently hydroxylated to methylazoxymethanol (MAM). These processes occur mostly in the liver, and the hydroxylation step is mediated by cytochrome P450 enzymes. MAM is chemically unstable and can spontaneously decompose to formaldehyde, water and nitrogen. In this decomposition, the methyldiazonium ion is formed, which can alkylate DNA and increase the risk of mismatched bases.

Adverse effects Chronic exposure of symmetrical dimethylhydrazine led to adverse effects in multiple organs in animals, but its most prominent effect is carcinogenicity. This has been reported in several animal experiments, including rats and mice. 1,2-dimethylhydrazine is classified as a category 2 carcinogen, meaning that there is a significant probability that it can cause cancer in humans as well.

Use and exposure risk Symmetrical dimethylhydrazine is mainly used experimentally for its carcinogenic properties, particularly to induce colon cancer in laboratory animals for cancer research. Its isomer, unsymmetrical dimethylhydrazine, is widely used in rocket fuel. Because symmetrical dimethylhydrazine is not used commercially, it is unlikely to be released into the environment in large volumes. When released into the air, hydrazine compounds are relatively quickly decomposed by reactive compounds in the air. Also, in soil or water hydrazines usually do not persist for longer than a few weeks. Human exposure is therefore unlikely. Laboratory staff that works with the compound would be most at risk. It might also be possible to come into contact through hazardous waste sites, although unlikely.

Molecular mechanism of action Symmetrical dimethylhydrazine is an indirect-acting genotoxin, meaning its carcinogenicity depends on the metabolization to methyldiazonium ions. Methyldiazonium is a strong methylating agent due to its electrophilic nature and can methylate nucleotide bases in DNA. Methylation occurs most frequently at the N7 or O6 sites of guanine, but it can also methylate at the C8 site of guanine and at the N3 site of adenine, as well as at the O4 site of thymine. The methylated base may mispair during DNA replication. For example, methylated guanine can pair with thymine, instead of cytosine. This is followed by subsequent replication, which leads to further mispairing and could mutate a GC pair to an AT pair. When mutations occur in certain genes a neoplasm can be initiated.

Toxicology data The International Agency for Research on Cancer (IARC) has classified symmetrical dimethyl hydrazine as part of group 2A of the carcinogenesis classification, meaning it is probably carcinogenic to humans. Although the effects of symmetrical dimethyl hydrazine have not been studied on humans in vivo, there is sufficient evidence acquired from animal studies. Similar patterns of DNA damage in humans and a wide range of animals have been observed in vitro, caused by dimethyl hydrazine. The ILO-WHO International Chemical Safety Cards (ICSCs) warns that symmetrical dimethyl hydrazine can be absorbed into the body by inhalation, ingestion and possibly through the skin contact. Depending on the route of exposure and on the species tested, the LD50 ranged from tens to several hundred mg/kg. The primary target appears to be the intestines, where morphological and biochemical changes have been observed in the intestinal epithelium after subcutaneous injection.

References

Illustrations

Worked examples

Example 1 — a first encounter with Symmetrical dimethylhydrazine

Start with the simplest possible case. Write down what Symmetrical dimethylhydrazine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Symmetrical dimethylhydrazine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Symmetrical dimethylhydrazine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Symmetrical dimethylhydrazine

In research: Symmetrical dimethylhydrazine appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Symmetrical dimethylhydrazine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Symmetrical dimethylhydrazine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hydrazines, IARC Group 2A carcinogens, Methylating agents, so understanding it makes those chapters shorter.
In everyday life: Look for Symmetrical dimethylhydrazine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Symmetrical dimethylhydrazine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Symmetrical dimethylhydrazine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Symmetrical dimethylhydrazine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Symmetrical dimethylhydrazine in simple terms?

Symmetrical dimethylhydrazine (SDMH), or 1,2-dimethylhydrazine, is the organic compound with the formula (CH3NH)2. It is one of the two isomers of dimethylhydrazine.

Why does Symmetrical dimethylhydrazine matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Symmetrical dimethylhydrazine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Symmetrical dimethylhydrazine.