Groups, withdrawal

Methyl group releases electrons stabilizes carbocation than than Tnfluoromethyl group withdraws electrons destabilizes carbocaUon... 

The carbonyl group withdraws rr electron density from the double bond and both the carbonyl carbon and the p carbon are positively polarized Their greater degree of charge separation makes the dipole moments of a p unsaturated carbonyl compounds signifi cantly larger than those of comparable aldehydes and ketones... 

Methyl group releases electrons, stabilizes carbocation than than Trifluoromethyl group withdraws electrons, destabilizes carbocation... 

Note again that halogens, hydroxyl, alkoxyl, and amino groups withdraw electrons inductively and donate electrons by resonance. Halogens have a... 

The electronegative O atoms of the carboxylic acid group withdraw electrons from the whole ring, thereby reducing its overall electron density. Moreover, resonance preferentially removes electrons from the ortho and para positions. To focus on the essentials, only the lone pairs of electrons involved in resonance are shown ... 

CSline. CSline [84] provides information on well-designed and well-executed clinical trials of drugs currently under study or in use in humans. This information includes study objectives, design, population, intervention groups, withdrawals, adverse reactions, endpoints and results, conclusions, and references. The CSline database covers more than 500 drugs currently on the market or in development. Pharmacological data from more than 2000 journal articles, congresses, and books are added each year. The product is commercially available on CD-ROM from Prous Science and is updated every 2 months. 

Wouters EF, Postma DS, Fokkens B, Hop WC, Prins J, Kuipers AF, Pasma HR, Hensing CA, Creutzberg EC, COSMIC (COPD and Seretide a Multi-Center Intervention and Characterization) Study Group. Withdrawal of fluticasone propionate from combined sahneterol/fluticasone treatment in patients with COPD causes immediate and sustained disease deterioration a randomised controlled hial. Thorax 2005 60(6) 480-7. 

Sometimes individual treatment may be used in conjunction with a short group approach either before or after the group withdrawal course. It seems appropriate to offer one to two individual sessions (not in the client s home but preferably at the place where the group will be held) before the course starts for clients who are agoraphobic, if that treatment option is on... 

Trifluoromethyl group withdraws electrons, destabilizes carbocation... 

A is correct. The carbonyl group withdraws negative charge, stabilizing the conjugate base of pyruvate,... 

Two electronic effects are operating in this case an inductive effect and a resonance effect. Because of the high electronegativity of the oxygen, the methoxy group withdraws electrons by its inductive effect (see Section 4.5). If this were the only effect operating,... 

Despite the fact that the aldehyde group withdraws electron density from positions 2 and 6, C6 is still the position for nitration. The activating methoxy groups dominate electronically and the choice is really between C2, C5, and C6. Now consider steric factors—the -OMe groups block the positions ortho to them more than the carbonyl does because reaction at C2 or C5 would lead to three adjacent substituents which is why substitution occurs at position 6. 

Diethyl malonate adds to diethyl fumarate in a conjugate addition reaction promoted by sodium ethoxide in dry ethanol to give a tetraester, Diethyl fumarate is an excellent Michael acceptor because two ester groups withdraw electrons from the alkene, The mechanism involves deprotonation of the malonate, conjugate addition, and reprotonation of the product enolate by ethanol solvent, In this reaction two ester groups stabilize the enolate and two more promote conjugate addition. 

All deactivating groups withdraw electrons from a ring. 

The acidity of substituted benzoic acids is dependent on the relative ability of the substituent to donate or withdraw electron density. The more strongly a group withdraws electrons, the greater is the acidity. Thus the order of increasing acid strength is 4-hydroxybenzoic acid < benzene-1,4-dicarboxylic acid < 4-acetyl-benzoic acid < 4-cyanobenzoic acid... 

N-Aryl substituents usually depress the basic properties of the imidazole or benzimidazole nucleus. The effects of substituents on the aryl group are evident from the data listed in Table 7 which also lists rate constants for quaternization with iodoethane, a reaction which is dependent upon the nucleophilic character of the pyridine-type nitrogen (70CHE194). A phenyl group withdraws electrons from the imidazole ring, but does so rather weakly. The p value of +0.753 for the protonation process is in accord with weak electron transfer from the phenyl substituent to the basic nitrogen. 

Considering inductive effects only, an NH2 group withdraws electron demsity and CH3 donates electron density. 

For example, seven resonance structures can be drawn for benzaldehyde (C HsCHO). Because three of them place a positive charge on a carbon atom of the benzene ring, a CHO group withdraws electron density from a benzene ring by a resonance effect. 

The -NH2 group donates electron density, making the benzene ring more electron rich (redder), whereas the -CHO group withdraws electron density, making the benzene ring less electron rich (greener). 

The activation by —NO2 and other electron-attracting groups can be accounted for, as we have seen, simply on the basis of inductive effects. However, it is generally believed that certain of these groups withdraw electrons by resonance as well. Let us see what kind of structures are involved. 

Since a CF3 group withdraws electrons only in an inductive manner, insertion of a methylene group between CF3 and C02H moieties naturally diminishes its inductive effect. 

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