Imide

Key takeaways

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

Reference excerpt

In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis. In terms of commercial applications, imides are best known as components of high-strength polymers, called polyimides. Inorganic imides are also known as solid state or gaseous compounds, and the imido group (=NH) can also act as a ligand.

Examples The simplest example is diacetamide with the formula HN(COCH3)2, formally the diacetylated derivative of ammonia. Common imides are cyclic, formally derived from dicarboxylic acids and ammonia. The names of these cyclic imides reflect the parent acid; e.g. succinimide from succinic acid:

Many imides are derived from primary amines as opposed to ammonia. These are indicated by N-substituent in the prefix. For example, N-ethylsuccinimide is derived from succinic acid and ethylamine.

Physical properties Being highly polar, imides exhibit good solubility in polar organic solvents. Unlike the structurally related acid anhydrides, they resist hydrolysis and some can even be recrystallized from boiling water. The N–H center for imides derived from ammonia is acidic and can participate in hydrogen bonding. The N-H group is weakly acidic as indicated in the case of maleimide, with a pKa estimated at 10.

Occurrence and applications Many high strength or electrically conductive polymers contain imide subunits, i.e., the polyimides. One example is Kapton where the repeat unit consists of two imide groups derived from aromatic tetracarboxylic acids. Another example of polyimides is the polyglutarimide typically made from polymethylmethacrylate (PMMA) and ammonia or a primary amine by aminolysis and cyclization of the PMMA at high temperature and pressure, typically in an extruder. This technique is called reactive extrusion. A commercial polyglutarimide product based on the methylamine derivative of PMMA, called Kamax, was produced by the Rohm and Haas company. The toughness of these materials reflects the rigidity of the imide functional group. Interest in the bioactivity of imide-containing compounds was sparked by the early discovery of the high bioactivity of the Cycloheximide as an inhibitor of protein biosynthesis in certain organisms. Thalidomide, famous for its adverse effects, is one result of this research. A number of fungicides and herbicides contain the imide functionality. Examples include Captan, which is considered carcinogenic under some conditions, and Procymidone.

In the 21st century new interest arose in thalidomide's immunomodulatory effects, leading to the class of immunomodulators known as immunomodulatory imide drugs (IMiDs).

Preparation Most common imides are prepared by heating dicarboxylic acids or their anhydrides and ammonia or primary amines. The result is a condensation reaction:

(RCO)2O + R′NH2 → (RCO)2NR′ + H2O These reactions proceed via the intermediacy of amides. The intramolecular reaction of a carboxylic acid with an amide is far faster than the intermolecular reaction, which is rarely observed. They may also be produced via the oxidation of amides, particularly when starting from lactams.

R(CO)NHCH2R' + 2 [O] → R(CO)N(CO)R' + H2O Certain imides can also be prepared in the isoimide-to-imide Mumm rearrangement.

Reactions For imides derived from ammonia, the N–H center is weakly acidic. Thus, alkali metal salts of imides can be prepared by conventional bases such as potassium hydroxide. The conjugate base of phthalimide is potassium phthalimide. These anion can be alkylated to give N-alkylimides, which in turn can be degraded to release the primary amine. Strong nucleophiles, such as potassium hydroxide or hydrazine are used in the release step. Treatment of imides with halogens and base gives the N-halo derivatives. Examples that are useful in organic synthesis are N-chlorosuccinimide and N-bromosuccinimide, which respectively serve as sources of "Cl+" and "Br+" in organic synthesis. With base followed by acid, cyclic imides open to give amido-acids. Thus, maleamic acid (HO2CCH=CHC(O)NH2) is derived from maleimide, succinamic acid (HO2CCH2CH2C(O)NH2) from succinimide, phthalimidic acid HO2CC6H4C(O)NH2 from phthalimide.

Related compounds Organic compounds called carbodiimides have the formula RN=C=NR. They are unrelated to imides. Acylureas are imides, but where one acyl group is in fact a carbamoyl: R-C(=O)-NH-C(=O)NH2.

Isoimides Isoimides are isomeric with imides and have the formula RC(O)OC(NR′)R″. They are often intermediates that convert to the more symmetrical imides. Isoimides upon heating rearrange to imides:

RC(O)OC(NR′)R → [RC(O)]2NR′

References

External links IUPAC: imides

Illustrations

Worked examples

Example 1 — a first encounter with Imide

Start with the simplest possible case. Write down what Imide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, 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 Imide 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 Imide 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 Imide

In research: Imide appears in mathematics 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 Imide 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: Imide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Functional groups, Imides, so understanding it makes those chapters shorter.
In everyday life: Look for Imide 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.

How to study Imide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Imide 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 Imide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Imide in simple terms?

In organic chemistry, an imide is a functional group consisting of two acyl groups bound to nitrogen. The compounds are structurally related to acid anhydrides, although imides are more resistant to hydrolysis.

Why does Imide matter?

Because it connects several mathematics 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 Imide?

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 Imide.