まとめ
マーチソン隕石の有機ポリマーは酸化時にメタヒドロキシフェノール酸を産生し,パラヒドロキシ誘導体を産生する地上のポリマーとは違います. これは,地球外生命の起源が太陽星雲のフィッシャー・トロプシュ反応から来ている可能性を示唆している.
科学分野:
- アストロケミストリー アストロケミストリー
- オーガニック・ジオケミストリー オーガニック・ジオケミストリー
- 宇宙化学 (コスモケミストリー)
背景:
- マーチソンC2コンドライトのような隕石には,複雑な有機物質が含まれています.
- 地球外生物の有機分子の起源と構成を理解することは,天体生物学にとって極めて重要です.
- リンニンやヒュミック酸のような地上の有機ポリマーは,比較のための基準となる.
研究 の 目的:
- マーチソン隕石内の有機ポリマーを分析するために.
- 隕石の有機ポリマーから派生したフェノール化合物を識別するために.
- 隕石ポリマーの酸化産物を地上の同類物と比較する.
主な方法:
- ムルチソン隕石の有機ポリマーをアルカリ性銅酸化物を使って酸化する.
- 合成されたフェノール酸および非フェノール酸の識別と特徴付け.
- 得られた化合物を,地上のポリマー酸化による化合物と比較.
主要な成果:
- 7つのフェノル酸,特にメタ-ヒドロキシ (3-ヒドロキシ) ベンゾ酸と3-ヒドロキシ-1,5-ベンゼン-ディカルボキシル酸が特定されました.
- フェノル酸は,ポリマー内のフェノルエーテルから由来すると推測されています.
- 陸上のポリマーは,同一の条件下で,主にパラヒドロキシベンゼン誘導体を生成した.
結論:
- メタヒドロキシフェノール酸の構造は,マーチソンポリマーの地球外の起源を示唆しています.
- ポリマーのフェノールエーサーは,太陽の星雲の中のCOとH2からフィッシャー・トロプシュ型反応によって形成された可能性が高い.
- この発見は,地球外の有機物質と,地上のポリマーであるリグニンやヒュミック酸を区別している.
関連する概念動画
01:13Olefin Metathesis Polymerization: Overview
Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...
02:35Ethers from Alkenes: Alcohol Addition and Alkoxymercuration-Demercuration
Overview
Ethers can also be prepared from alkenes through acid-catalyzed addition of alcohols and alkoxymercuration–demercuration.
Preparation of Ethers by Acid-Catalyzed Addition of Alcohol to Alkenes
The acid-catalyzed addition of alcohol to an alkene involves treating the alkene with an excess of alcohol in the presence of an acid catalyst to form an ether under suitable conditions. The hydrogen will add to the less substituted carbon so that the nucleophile can attack the more substituted...
Ethers can also be prepared from alkenes through acid-catalyzed addition of alcohols and alkoxymercuration–demercuration.
Preparation of Ethers by Acid-Catalyzed Addition of Alcohol to Alkenes
The acid-catalyzed addition of alcohol to an alkene involves treating the alkene with an excess of alcohol in the presence of an acid catalyst to form an ether under suitable conditions. The hydrogen will add to the less substituted carbon so that the nucleophile can attack the more substituted...
02:28Structure and Nomenclature of Ethers
Structure and Bonding
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two — identical or different — alkyl, aryl, or vinyl groups. The C–O–C linkage in dimethyl ether — the simplest ether — has an approximately tetrahedral bond angle of 110.3 degrees. The oxygen atom is sp3- hybridized, with the C–O distance being about 140 pm.
Classification of Ethers
Based on their attached substituent groups, ethers can be classified into two...
Ethers are organic compounds with an ether functional group which is characterized by an oxygen atom connected to two — identical or different — alkyl, aryl, or vinyl groups. The C–O–C linkage in dimethyl ether — the simplest ether — has an approximately tetrahedral bond angle of 110.3 degrees. The oxygen atom is sp3- hybridized, with the C–O distance being about 140 pm.
Classification of Ethers
Based on their attached substituent groups, ethers can be classified into two...
00:53Olefin Metathesis Polymerization: Acyclic Diene Metathesis (ADMET)
Acyclic diene metathesis polymerization or ADMET polymerization involves cross-metathesis of terminal dienes, such as 1,8-nonadiene, to give linear unsaturated polymer and ethylene. As ADMET is a reversible process, the formed ethylene gas must be removed from the reaction mixture to complete the polymerization process.
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
Similar to cross-metathesis, ADMET also involves the formation of metallacyclobutane intermediate by [2+2] cycloaddition of one of the double bonds of a terminal diene with...
02:23Autoxidation of Ethers to Peroxides and Hydroperoxides
Ethers represent a class of chemical compounds that become more dangerous with prolonged storage because they tend to form explosive peroxides when standing in the air. Autoxidation is the spontaneous oxidation of a compound in air. In the presence of oxygen, ethers slowly oxidize to form hydroperoxides and dialkyl peroxides.
02:18Ethers to Alkyl Halides: Acidic Cleavage
Ethers are generally unreactive and unsuitable for direct nucleophilic substitution reactions since the alkoxy groups are strong bases and, therefore, poor leaving groups. However, ethers readily undergo acidic-cleavage reactions. Ethers can be converted to alkyl halides when heated with strong acids such as HBr and HI in a sequence of two substitution reactions.