Ethyl anion

Write the equation for the reaction of 1 hexyne with ethyl magnesium bromide as if it involved ethyl anion (CH3CH2 ) instead of CH3CH2MgBr and use curved arrows to represent the flow of electrons j... 

Problem 14 7 at the end of the preceding section intro duced this idea with the sug gestion that ethylmagnesium bromide be represented as ethyl anion... 

Fig. 8. Sensitizing dyes of the cyanine class. K. = N — alkyl or chalcogens (O, S, Se, Te) R = chloro, phenyl, or additional benzene ring R = methyl, ethyl, or hydrogen n = 0, 1, 2 and RPRIME, R " = alkyl or sulfoalkyl. Solubihty in methanol for a carbocyanine dye n = 1 X = S R = Cl R = ethyl. Cationic dye (R" = R " = ethyl anion = bromide) 9.5 mmol/T. neutral dye (R" = ethyl R " = sulfopropyl) 3.6 mmol/L anionic dye (R" = R = sulfopropyl ...

Ethyl anion 1-Hexyne Ethane Conjugate base of 1-hexyne... 

CH3CH2 (Ethyl anion) (Increasing basicity of the conjugate base)... 

The position of equilibrium lies to the right. Ethyl anion is a very powerful base and depro-tonates acetylene quantitatively. 

Ethyl anion reacts as a Br0nsted base to remove a proton from the alkyne. The proton at C-l is removed because it is the most acidic, having a pof approximately 25. 

The fact that the w orbital drops drastically on bending is, of course, related to the fact that the vinyl anion (sp2 lone pair) is more stable than the ethyl anion (higher energy sp3 lone pair). That is, upon bending, more s character is mixed into the LUMO of the alkyne, which ultimately becomes the sp2 anion lone pair upon addition of a nucleophile. However, our treatment also explains why nucleophilic attack on alkynes is preferred even for early transition states or for those reactions, such as cycloadditions and thermal rearrangements, in which anions are not formed. 

A simple HMO calculation for the cyclization of the allylcarbinyl to the cyclopropylcarbinyl anion (161) has appeared (equation 33) and, based on proton affinities, 161 was calculated to be 10 kcal mol" more stable than ethyl anion (SCF double-zeta basis) and 14.3 kcal mol" more stable than i-PrCH (STO-3G). The bisected geometry was predicted to be most stable, with electron donation from the filled p orbital at C(4) to the unoccupied Walsh 4ai MO (162) at C(l). Inductive electron withdrawal by cyclopropyl would also stabilize this anion. 

While the plots of enthalpies of formation indicate that the arsenic, antimony and bismuth data are problematic, they cannot be used to recommend alternative values since both the methyl and ethyl are thought to be affected by large errors. If one of these were known to be reliable, it could be used to predict the second one. The difference between the enthalpies of formation of methyl and ethyl derivatives relates to the electronegativity of the affixed atom or group, wherefore the more electronegative it is, the less relatively stable is the methyl compared to the ethyl derivative. This stability reasoning extends to the relative stability of methyl and ethyl cation, and antithetically to methyl and ethyl anion, hence we conclude that only for extremely electropositive elements such as lithium is it at all conceivable that the methyl compound has the more... 

In the ethyl anion, CH3CH2, suggest the shape of this charged species and also indicate what... 

Methyl anion Ethyl anion sec-Propyl anion tert-Butyl anion... 

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