(Z) -ペント-2-エン-4-イネニトリルとマレニニトリルのマイクロ波スペクトルと分子構造
R J Halter1, R L Fimmen, R J McMahon
1Department of Chemistry, University of Wisconsin, Madison, WI 53706-1396, USA.
Journal of the American Chemical Society
|December 6, 2001
まとめ
(Z) -pent-2-en-4-ynenitrileとmaleonitrileの正確な分子構造は,マイクロ波スペクトル検査と量子化学を用いて決定されました. これらの発見は,星間不飽和分子の洞察を提供します.
科学分野:
- 物理化学 物理化学
- 量子化学とは,量子化学である.
- スペクトル顕微鏡検査です.
背景:
- 正確な分子構造は,化学的性質と恒星間過程を理解するために不可欠です.
- 以前の研究は,関連する不飽和分子に焦点を当てていましたが,特定のシアノポリエインの正確な均衡構造は欠けていました.
研究 の 目的:
- (Z) -pent-2-en-4-ynenitrileとmaleonitrileの正確な均衡構造を決定するために.
- これらの構造を関連分子と比較し,線形性からの偏差を調査する.
主な方法:
- 複数の同位体によるマイクロ波スペクトロスコピーを用いた.
- 実験データを裏付けるために,CCSD(T) /cc-pVTZを含む初期量子化学計算が使用されました.
- 振動-回転相互作用の効果は,計算された力場を用いて計算された.
主要な成果:
- (Z) -pent-2-en-4-ynenitrileとmaleonitrileの正確な均衡の幾何学的なパラメータが得られました.
- 決定された構造は,高レベルのアビニシオ計算と密接に一致しました.
- 幾何学的なパラメータは,2つの分子と (Z) -ヘックス-3-エネ-1,5-ディイネ.との間の類似性を示しました.
- アルキンとシアノの結合において,線形性からのわずかな偏差が観察されました.
結論:
- この研究は,2つの重要なシアノポリエンの正確な均衡構造を成功裏に決定しました.
- この発見は,ラジオ天文学と恒星間化学のための貴重なデータを提供します.
- この結果は,宇宙における不飽和種の形成と行動を理解するのに寄与する.
関連する概念動画
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:23Mass Spectrum
A mass spectrum is the graphical representation of the relative abundance of the charged fragments in an analyte plotted against their mass-to-charge ratio (m/z). The plot's x-axis represents the ratio of the mass of the charged fragment to the number of charges it carries. The y axis of the plot represents the relative abundance of each charged species. The relative abundance is calculated from the signal intensity of each charged species recorded at the detector. The most intense signal (the...
01:28Structures of Carboxylic Acid Derivatives
Structure of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the unhybridized p...
00:59Mass Spectrometry: Alkene Fragmentation
Alkenes lose one electron from the unsaturated π bond upon ionization and form stable molecular ions. Further fragmentation of alkenes occurs through three different reaction pathways. The most prominent fragmentation is the cleavage at the allylic position. The resultant allylic carbocation is resonance stabilized. In the mass spectra of terminal alkenes, this fragment appears at a mass-to-charge ratio of 41. In the internal alkenes, where there are two choices of allylic cleavage, the...
01:01Mass Spectrometry: Carboxylic Acid, Ester, and Amide Fragmentation
The fragmentation patterns observed for compounds such as carboxylic acids, esters, and amides in the mass spectra include ⍺-cleavage and McLafferty rearrangement. Fragmentation by ⍺-cleavage preferentially occurs at the carbon-carbon bond at the ⍺-position next to the carboxylic group to generate a neutral radical and a cation. Long chain compounds with hydrogen at their γ-carbon undergo McLafferty rearrangement to give a radical cation and a neutral alkene.
For example, the fragmentation of...
For example, the fragmentation of...
01:24Mass Spectrum: Interpretation
An unknown compound can be established by identifying the molecular ion peak in the mass spectrum. The molecular ion peak is often weak or absent due to the predominance of fragmentation in high-energy electron beams. In such cases, a soft-energy electron beam can be used to scan the spectrum to enhance the intensity of the molecular ion peak. Additionally, chemical ionization, field ionization, and desorption ionization spectra are used to obtain a relatively intense molecular ion peak.To...