大型のトリアゾリン結晶の光誘導および熱脱窒化:固体から固体への変換の洞察
Denisse de Loera1, Antoine Stopin, Miguel A Garcia-Garibay
1Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
Journal of the American Chemical Society
|April 4, 2013
まとめ
結晶型トリアゾリンを光誘導および熱による脱窒化により,クリーンな固体から固体への反応でアジリジンが得られます. これらの反応は,ユーテクティックとガラスの移行点に相対的な温度によって影響される,転移安定段階または再構築段階の移行を経由して進行します.
科学分野:
- 有機化学 オーガニック・ケミストリー
- 固体化学 固体化学
- フォトケミストリー フォトケミストリー
背景:
- 結晶型トリアゾリンは窒素除去され,アジリジンを形成する.
- 固体から固体への反応は,ユニークなメカニズム的な経路を示します.
- 反応経路の制御は,効率的な合成に不可欠です.
研究 の 目的:
- 結晶型トリアゾリンにおける光誘導および熱誘導による脱窒素化のメカニズムを調査する.
- 固体反応における相変化の役割を理解する.
- 反応経路と熱的特性,例えばエウテクティックおよびガラス化移行温度を相関させるため.
主な方法:
- 構造分析のための粉末X線微分法 (PXRD)
- 化学および構造的モニタリングのための固体 (13) C CPMAS NMRおよびFTIRスペクトロスコーピー.
- 熱分析 (DSC/TGA) で,相変化温度を測定する.
主要な成果:
- 結晶型トリアゾリンから固体対固体反応によるアジリジンの定量形成.
- 観察された反応経路には,転移安定相の形成または再建的相移行が含まれています.
- 固体から固体への変換は,ユーテクティック温度以下で好まれ,ガラスの移行温度以上の再構築的移行を含む場合があります.
結論:
- 結晶型トリアゾリンの脱窒素化は,固体変異を経由してアジリジンへのクリーンな経路を提供します.
- アモルフィゼーションと再構築的移行を含む相行動が,反応機構を決定する.
- 温度に依存する相変遷を理解することは,固体反応の結果を制御する上で鍵となる.
関連する概念動画
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
01:16Cycloaddition Reactions: MO Requirements for Thermal Activation
Thermal cycloadditions are reactions where the source of activation energy needed to initiate the reaction is provided in the form of heat. A typical example of a thermally-allowed cycloaddition is the Diels–Alder reaction, which is a [4 + 2] cycloaddition. In contrast, a [2 + 2] cycloaddition is thermally forbidden.
01:17Thermal Electrocyclic Reactions: Stereochemistry
The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
01:19Diazonium Group Substitution: –OH and –H
Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.
01:371° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
01:17Ziegler–Natta Chain-Growth Polymerization: Overview
Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...