chemistry

Grepafloxacin

Grepafloxacin 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 Grepafloxacin rather than just read about it. In short: Grepafloxacin (trade name Raxar, Glaxo Wellcome) was an oral broad-spectrum fluoroquinolone antibacterial agent used to treat bacterial infections. Grepafloxacin was withdrawn worldwide from markets in 1999, due to the drug's potential to cause a potentially fatal cardiac arrhythmia.

Key takeaways

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

Reference excerpt

Grepafloxacin (trade name Raxar, Glaxo Wellcome) was an oral broad-spectrum fluoroquinolone antibacterial agent used to treat bacterial infections. Grepafloxacin was withdrawn worldwide from markets in 1999, due to the drug's potential to cause a potentially fatal cardiac arrhythmia.

Clinical uses Grepafloxacin was used for treating exacerbations of chronic bronchitis caused by susceptible bacteria (e.g. Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis), community-acquired pneumonia (including those, in addition to the above germs, caused by Mycoplasma pneumoniae) gonorrhea and non-gonococcal urethritis and cervicitis (for example caused by Chlamydia trachomatis or Ureaplasma urealyticum).

Synthesis The preparation of quinolones bearing a substituent at position 5 is complicated by the greater electrophilic character of the 8 position. One scheme for resolving the problem consists in blocking access to position 8 by first adding a readily removable group to that center.

The scheme starts with the conversion of the carboxylic acid in (1) to its dimethyloxazoline derivative (3) by reaction with the aminomethyl propanol (2). Lithium diisopropylamide (LDA) then removes a proton from the 8 position; treatment of that anion with trimethylsilyl iodide leads to the silylated intermediate (4). A second round of LDA then generates a carbanion at the only open position; reaction with methyl iodide leads to the corresponding 5 methyl derivative (5). Treatment of that product with cesium fluoride breaks the carbon–silicon bond, removing the silyl group; aqueous acid then hydrolyzes the oxazoline to afford the free acid (6). This last intermediate is then taken on to the quinolone (9) by essentially the same scheme as that used to prepare difloxacin, with the difference that the chain elongation is by means of Grignard reagent of ethyl bromoacetate. Treatment of (9) with 2-methylpiperazine proceeds by reaction at the less hindered of the two amino groups; saponification then affords grepafloxacin (10).

Stereochemistry Grepafloxacin contains a stereocenter and consists of two enantiomers. This is a racemate, ie a 1: 1 mixture of (R)- and the (S)-forms:

Illustrations

Worked examples

Example 1 — a first encounter with Grepafloxacin

Start with the simplest possible case. Write down what Grepafloxacin 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 Grepafloxacin 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 Grepafloxacin 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 Grepafloxacin

In research: Grepafloxacin 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 Grepafloxacin 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: Grepafloxacin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Carboxylic acids, Cyclopropyl compounds, Fluoroquinolone antibiotics, so understanding it makes those chapters shorter.
In everyday life: Look for Grepafloxacin 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 Grepafloxacin in 20 minutes

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

Frequently asked questions

What is Grepafloxacin in simple terms?

Why does Grepafloxacin 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 Grepafloxacin?

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 Grepafloxacin.