Name: selective mno2 oxidation of alcohols
Uploaded: 2025-05-22T09:05:43.000Z
Duration: 1 min 21 s
Channel: JoVE

تخضع الكحوليات الأليليك والبنزيلية لأكسدة انتقائية بواسطة ثاني أكسيد المنغنيز المنشط (IV) عبر وسيط جذري.
تعطي الكحوليات الأليلية الأولية الألدهيدات ، وتشكل الكحوليات الأليلية الثانوية الكيتونات.
يتم تحضير MnO2 المنشط عن طريق تفاعل اختزال الأكسدة عندما يتفاعل ملح Mn + 2 ، مثل كبريتات المنغنيز ، مع برمنجنات البوتاسيوم.
يمكن فهم الانتقائية العالية ل MnO2 تجاه الكحول الآليلي والبنزيلي من آلية التفاعل.
تضيف مجموعة الهيدروكسيل من الكحول في البداية إلى MnO2 لتشكيل إستر.
بعد ذلك ، يقبل Mn (IV) إلكترونا ، ويتم نقل ذرة الهيدروجين من الكربون الأليليك أو البنزيلي إلى الأكسجين المتصل بالمنغنيز.
هذا يقلل من Mn (IV) إلى Mn (III) ، مما يعطي جذر كربوني أليليك أو بنزيلي ، والذي يتم تثبيته بالرنين.
أخيرا ، تؤدي إعادة ترتيب الإلكترون الإضافية إلى تقليل Mn (III) إلى Mn (II) جنبا إلى جنب مع تكوين منتج الألدهيد أو الكيتون.
والجدير بالذكر أنه أثناء الأكسدة الجذرية ، يظل الكحول غير البنزيلي غير متأثر.

<ol>
	<li>لودون ، إم ، وباريس ، ج. (2016). الكيمياء العضوية. نيويورك ، نيويورك: نشر ماكميلان ، 851-852.</li>
	<li>كلاين ، د. (2017). الكيمياء العضوية. نيو جيرسي ، نيوجيرسي: وايلي ، 462.</li>
</ol>

الأكسدة الجذرية للكحول الأليليك والبنزيلي

Radical Oxidation of Allylic and Benzylic Alcohols

<div style="direction:rtl">يمكن لأكسيد المنغنيز (IV) المنشط أكسدة كحولات الأليلك والبنزيلي بشكل انتقائي عبر آلية وسيطة جذرية. تتأكسد الكحولات الأليلية الأولية إلى ألدهيدات، في حين تنتج الكحولات الأليلية الثانوية الكيتونات. تفاعل الأكسدة والاختزال لبرمنجنات البوتاسيوم مع ملح المنغنيز (II) مثل كبريتات المنغنيز (تحت الظروف القلوية أو الحمضية)، يليه تجفيف شامل، ينتج العامل المؤكسد: MnO2 المنشط. في حين أن MnO2 غير قابل للذوبان في المذيبات المستخدمة للتفاعل، فإن أكسدة كحولات الأليلك والبنزيلي تحدث على سطح MnO2. ولأن الماء يتنافس مع الكحول على المواقع النشطة في MnO2، فيجب إزالته بالتجفيف. تعتبر الأكسدة الجذرية بواسطة MnO2 انتقائية، ولا يؤثر الكاشف على الكحولات غير البنزيلية أو غير الأليلية. في البداية، تضاف مجموعة الهيدروكسيل من الكحول إلى MnO2 لتكوين الإستر. بعد ذلك، يقبل المنغنيز (IV) إلكترونًا، ويتم نقل ذرة الهيدروجين من الكربون الأليلي أو البنزيلي إلى الأكسجين المرتبط بالمنجنيز. وهكذا يتم اختزال Mn(IV) إلى Mn(III)، مما ينتج عنه جذر كربون أليلي أو بنزيلي، وهو ثابت بالرنين. إن زيادة ثبات هذا الوسيط الجذري البنزيلي/الأليلي، مقارنة بثبات الوسيط المتكون من كحولات غير بنزيلية أو غير أليلية، يزيد من معدل هذه الخطوة ويعزز الانتقائية. يؤدي المزيد من إعادة ترتيب الإلكترون إلى اختزال المنغنيز (III) إلى المنغنيز (II) وينتج الألدهيد أو الكيتون.</div>

يمكن لأكسيد المنغنيز المنشط (IV) أن يؤكسد بشكل انتقائي الكحول الآليك والبنزيلي عبر آلية وسيطة جذرية. الكحول الأليلك الأولي هو ...

radical-oxidation-of-allylic-and-benzylic-alcohols

Education

JoVE Core

Organic Chemistry

الكيمياء العضوية

Unit 1

الوحدة الأولى

Radical Chemistry

الكيمياء الجذرية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

selective mno2 oxidation of alcohols

Activated manganese(IV) oxide, or MnO2, is a selective oxidizing agent for allylic and benzylic alcohols. It changes primary allylic alcohols into aldehydes and secondary allylic alcohols into ketones. The reaction happens by a radical pathway, so the carbon next to the alcohol group plays a key role.

The oxidizing agent is made from the redox reaction of potassium permanganate with an Mn(II) salt such as manganese sulfate. This can be done under alkaline or acidic conditions. After that, the material must be dried well to give activated MnO2. Water competes with alcohol for the active sites on MnO2, so removing water is important.

MnO2 is insoluble in the solvents used for this reaction. Even so, the oxidation takes place on the MnO2 surface. The reagent is selective and does not affect non-benzylic or non-allylic alcohols. First, the alcohol hydroxyl group adds to MnO2 to form an ester. Then Mn(IV) accepts an electron, and a hydrogen atom moves from the allylic or benzylic carbon to the oxygen attached to manganese.

This step reduces Mn(IV) to Mn(III) and forms a carbon radical. A radical is a species with an unpaired electron. The allylic or benzylic radical is resonance-stabilized, which means its electrons can spread out over more than one structure. That extra stability makes the reaction faster than for non-benzylic or non-allylic alcohols and helps explain the selectivity. Further electron rearrangement reduces Mn(III) to Mn(II) and gives the aldehyde or ketone.

Selective MnO2 Oxidation of Alcohols

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Alkyl Halide Reduction with Tributyltin Hydride

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key terms and concepts

See how activated MnO2 selectively oxidizes allylic and benzylic alcohols to aldehydes or ketones through a radical surface mechanism.

Selective MnO2 Oxidation of Alcohols | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

Selective MnO2 Oxidation of Alcohols

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