Thermodynamics is on our side

 Some of the syntheses we will meet will be quite surprisingly simple! It sometimes seems that we can just mix a few things together with about the right number of atoms and let thermo dynamics do the rest. A commercial synthesis of pyridines combines acetaldehyde and ammonia under pressure to give a simple pyridine. The yield is only about 50%, but what does that matter in such a simple process? By count ing atoms we can guess that four molecules of aldehyde and one of ammonia react, but exactly how is a triumph of thermodynamics over mechanism. Much more complex molecules can sometimes be made very easily too. Take allopurinol, for example, which you met in the last chapter. It is not too diffi cult to work out where the atoms go—the hydrazine obviously gives rise to the pair of adjacent nitrogen atoms in the pyrazole ring and the ester group must be the origin of the carbonyl group (the colours and numbers illustrate this)—but would you have planned this synthesis?

We will see that this sort of ‘witch’s brew’ approach to heterocyclic synthesis is restricted to a few basic ring systems and that, in general, careful planning is just as important here as elsewhere. The difference is that the synthesis of aromatic heterocycles is very forgiving—it often ‘goes right’ instead of going wrong. We’ll now look seriously at planning the synthesis of aromatic heterocycles.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم الشعائر يواصل تحضيراته لتنظيم عمل المواكب الحسينية في زيارة الأربعين

قسم شؤون المعارف يناقش تحضيرات المؤتمر العلمي الأول لمركز تراث البصرة

قسم الشؤون الفكرية يقيم دورة تطويرية لملاكات هيأة المساءلة والعدالة في الأرشفة الإلكترونية

المجمع العلمي ينظم مجلس عزاء في قضاء الهندية

المزيد

الآخبار الصحية

نصائح عملية للحد من التعرق المفرط في الصيف

أطباء يحذرون: مكمل غذائي شائع قد يدمر الجهاز العصبي

تحذير طبي من تأثير جانبي "غير متوقع" لحقن التخسيس

حمامات الثلج قد تكون خطيرة وأحيانا مميتة.. ما السبب؟

المزيد

الآخبار التكنلوجية

أكبر جدارية شمسية في العالم تدخل موسوعة غينيس.. مشروع ضخم

تسارع دوران الأرض يثير القلق.. وتحذيرات من "كوارث محتملة" ؟

"سوذبيز" تطرح أكبر قطعة من المريخ على الأرض في مزاد علني

أوبن أيه آي تعتزم إطلاق متصفح إنترنت يعمل بالذكاء الاصطناعي

المزيد

مواضيع ذات صلة

Aziridine: ring strain promotes ring opening

Reactions of saturated heterocycles

More heteroatoms in fused rings mean more choice in synthesis

Quinolones also come from anilines by cyclization to an ortho position

Quinolines and isoquinolines

Pyrimidines can be made from 1,3-dicarbonyl compounds and amidines

Pyrazoles and pyridazines from hydrazine and dicarbonyl compounds

There are thousands more heterocycles out there

Fusing rings to pyridines: quinolines and isoquinolines

Putting more nitrogen atoms in a six-membered ring

Benzo-fused heterocycles-Indoles are benzo-fused pyrroles

Five-membered rings with two or more nitrogen atoms Imidazole