Which of the following statements describes the first step in the mechanism
of the aldol condensation?
(a) An alpha hydrogen is abstracted by the base to form an enolate anion.
(b) A nucleophilic base attacks the carbonyl carbon atom.
(c) The carbonyl oxygen is protonated by the base ion.
(d) The alpha hydrogen is abstracted by an acid to the enolate anion.

1 Answer

Answer :

An alpha hydrogen is abstracted by the base to form an enolate anion

Related questions

Description : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The reaction between two molecules of acet

Last Answer : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The ... and 2,8-diketone D. All of these

Description : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The reaction between two molecules of acet

Last Answer : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The reaction ... )H-(CH_(2))_(4)-CH_(3)`

Description : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The reaction between two molecules of acet

Last Answer : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The ... and 2,8-diketone D. All of these

Description : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The reaction between two molecules of acet

Last Answer : Carbonyl compound which contains `alpha-H` gives aldol condenation reaction in presence of alkaline medium. The reaction ... )H-(CH_(2))_(4)-CH_(3)`

Description : Why do aldehydes undergo nucleophilic addition reactions while esters undergo nucleophilic acyl substitution reactions? (a) The carbonyl carbon of an ester is more electrophilic than that of an aldehyde. (b) ... adds to an aldehyde, neither H− nor R− can be eliminated since they are strongly basic

Last Answer : Once the nucleophile adds to an aldehyde, neither H− nor R− can be eliminated since they are strongly basic

Description : Base-catalyzed condensation of two ester molecules to form an alcohol and β-keto ester is called (a) Claisen condensation (b) Corey-House reaction (c) Aldol condensation (d) Transesterification

Last Answer : Claisen condensation

Description : Which of the following will undergo Aldol condensation? (a) Acetone (b) Benzaldehyde (c) Benzoic acid (c) Benzophenone

Last Answer : Acetone

Description : Acetone undergoes reduction with zinc amalgam in HCl to form propane. This reaction is known as (a) Clemmensen reduction (b) Wolf-Kishner reduction (c) Rosenmund reduction (d) Aldol condensation

Last Answer : Clemmensen reduction

Description : A 45-year-old solicitor had an onset of severe, crushing, substernal chest pain while attending a football match. He collapsed on his way to the car. Bystander Cardiorespiratory Resuscitation ... His oxyhemoglobin curve is shifted to the left 5) His pulmonary artery pressure is probably elevated

Last Answer : Answers-5 This young patient with severe central chest pain has probably arrested due to myocardial infarction and arrhythmia. His gases reveal high PO2 following 100% O2 but severe acidosis ... no left to right shunting and high pulmonary pressures would be expected after this arrest scenario.

Description : Why does methanal not give aldol condensation while ethanol gives ? 

Last Answer : Ans. This is because only those compounds which have hydrogen atoms can undergo  aldol reaction. Ethanol possesses -hydrogen and undergoes aldol condensation.   Methanal has no hydrogen atoms, hence does not undergo aldol condensation. 

Description : When formaldehyde is treated with 50% NaOH solution, it undergoes (a) Cannizzaro reaction (b) Wurtz reaction (c) Aldol condensation (d) Hydrolysis

Last Answer : Cannizzaro reaction

Description : The reaction of a sodium alkoxide with an alkyl halide is called (a) Wurtz-Fittig reaction (b) Perkin reaction (c) Williamson's synthesis (d) Aldol condensation

Last Answer : Williamson's synthesis

Description : The conversion of secondary alcohol to ketones in presence of aluminium isopropoxide and acetone as solvent is? a. Canizarro reaction b. Oppenauer oxidation c. Suzuki reaction d. Aldol Condensation

Last Answer : b. Oppenauer oxidation

Description : The carbon atom of a carbonyl group is (a) sp hybridized (b) sp2 hybridized (c) sp3 hybridized (d) None of these

Last Answer : sp2 hybridized

Description : Which of the following is not a correct statement concerning the FriedelCrafts acylation of benzene? (a) An alkyl group substitutes for a hydrogen. (b) The benzene ring attacks an acylium ion. (c) The acylium ion is resonance stabilized. (d) The acylium ion is often produced from an acyl chloride.

Last Answer : An alkyl group substitutes for a hydrogen

Description : Alpha particle is the nucleus of an atom of – (1) Lithium (2) Hydrogen (3) Helium (4) Oxygen

Last Answer : (3) Helium Explanation: Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is generally produced in the process of alpha decay.

Description : Alpha particle is the nucleus of an atom of (1) Lithium (2) Hydrogen (3) Helium (4) Oxygen

Last Answer : Helium

Description : In the scheme given below, the total number of intramolecular aldol condensation products formed from (Y) is

Last Answer : In the scheme given below, the total number of intramolecular aldol condensation products formed from (Y) is

Description : Total aldol condensation products (including stereosimers) formed by the reaction between acetaldehyde and acetophenone is :

Last Answer : Total aldol condensation products (including stereosimers) formed by the reaction between acetaldehyde and acetophenone is :

Description : Number of possible intra molecular aldol condensation product on heating with NaOH `H_(3)C-overset(O)overset(||)(C)-CH_(2)-CH_(2)-CH_(2)-overset(O)ove

Last Answer : Number of possible intra molecular aldol condensation product on heating with NaOH `H_(3)C-overset(O)overset(|| ... CH_(2)-overset(O)overset(||)(C)-H`

Description : (X) is the product of cross aldol condensation between benzaldehyde `(C_(6)H_(5)CHO)` and acetone. What is its structure ?

Last Answer : (X) is the product of cross aldol condensation between benzaldehyde `(C_(6)H_(5)CHO)` and acetone. What is its ... )-C=(CH_(3))_(2)` D. None of these

Description : Indicate the starting aldehyde or ketone from which each of the following compounds are formed by an aldol condensation reaction. (a)2-Ethyl-3-hydroxy

Last Answer : Indicate the starting aldehyde or ketone from which each of the following compounds are formed by an ... hexanal (b) 4-Hydroxy-4-methyl-2-pentanone

Description : Total aldol condensation products (including stereosimers) formed by the reaction between acetaldehyde and acetophenone is :

Last Answer : Total aldol condensation products (including stereosimers) formed by the reaction between acetaldehyde and acetophenone is :

Description : Number of possible intra molecular aldol condensation product on heating with NaOH `H_(3)C-overset(O)overset(||)(C)-CH_(2)-CH_(2)-CH_(2)-overset(O)ove

Last Answer : Number of possible intra molecular aldol condensation product on heating with NaOH `H_(3)C-overset(O)overset(|| ... CH_(2)-overset(O)overset(||)(C)-H`

Description : (X) is the product of cross aldol condensation between benzaldehyde `(C_(6)H_(5)CHO)` and acetone. What is its structure ?

Last Answer : (X) is the product of cross aldol condensation between benzaldehyde `(C_(6)H_(5)CHO)` and acetone. What is its ... )-C=(CH_(3))_(2)` D. None of these

Description : Indicate the starting aldehyde or ketone from which each of the following compounds are formed by an aldol condensation reaction. (a)2-Ethyl-3-hydroxy

Last Answer : Indicate the starting aldehyde or ketone from which each of the following compounds are formed by an ... hexanal (b) 4-Hydroxy-4-methyl-2-pentanone

Description : In an acid base reaction which product is produced along with a salt? (1) Hydrogen gas (2) Oxygen gas (3) Carbon dioxide (4) Water

Last Answer : (4) Water Explanation: When an acid and a base are placed together, they read to neutralize the acid and base properties, producing a salt. The H(+) cation of the acid combines with the OH(-) anion of the base to form water.

Description : Which of the following statements are true of oxidants? A. In addition to their pathophysiologic roles in inflammation, injury, and infection, oxidants also have physiologic roles. B. Oxidants may ... involved the catalytic production of superoxide anion (O 2 ) by the enzyme xanthine oxidase.

Last Answer : Answer: ABCD DISCUSSION: Oxidants are reactive oxygen metabolites that have both physiologic and pathophysiologic roles. As potent oxidizing agents, oxidants are involved in cytochrome P ... leukocyte infiltration and activation, causing further tissue damage by the release of cytotoxic proteases

Description : Nucleophilic part of the reagent attacks the substrate `CH_(3)CH_(2)COCH_(3)` on the :

Last Answer : Nucleophilic part of the reagent attacks the substrate `CH_(3)CH_(2)COCH_(3)` on the : A. carbon atom ... group C. methyl group D. `CH_(2)` group

Description : Chlorine free radicals react with methane by : (a) donating their free-radical electron to methane to form chloromethane. (b) abstracting a hydrogen atom from methane, and producing ... produce chloromethane. (d) forming a carbonium ion intermediate that rapidly dissociates to form chloromethane

Last Answer : abstracting a hydrogen atom from methane, and producing HCl and a methyl radical

Description : If the amino group and a carboxylic group of the amino acid are attached to same carbon atom, the amino acid is called as (A) Alpha (B) Beta (C) Gamma (D) Epsilon

Last Answer : Answer : A

Description : If the amino group and a carboxylic group of the amino acid are attached to same carbon atom, the amino acid is called (A) Alpha (B) Beta (C) Gamma (D) Delta

Last Answer : Answer : A

Description : All the following statements about renal tubular acidosis are correct except (A) Renal tubules may be unable to reabsorb bicarbonate (B) Renal tubules may be unable to secrete hydrogen ions (C) Plasma chloride is elevated (D) Anion gap is decreased

Last Answer : Answer : D

Description : Which of the following undergoes nucleophilic substitution exclusively by `S_(N^(1))` mechanism?

Last Answer : Which of the following undergoes nucleophilic substitution exclusively by `S_(N^(1))` ... Isopropyl chloride C. Chlorobenzene D. Benzyl chloride

Description : Alcohols are easily protonated than phenols. Justify.

Last Answer : Ans. In phenols lone pair of electrons on the oxygen atom are delocalised over the benzene ring due to resonance and hence are not easily available for protonation. In contrast in alcohols, ... oxygen atom are localized due to absence of resonance and hence are easily available for protonation. 

Description : In the anion `HCOO^(-)`, the two carbon-oxygen bonds are found to be equal length. What is the reason for it?

Last Answer : In the anion `HCOO^(-)`, the two carbon-oxygen bonds are found to be equal length. What is ... obtained by removal of a proton from the acid molecule

Description : What property of low-molecular weight aldehydes and ketones accounts for the magnitude of their boiling points? (a) The ability to form strong H-bonds between their molecules. (b) The ability of ... other polar molecules. (d) The ability of the carbonyl group to attract electrophiles and form bonds.

Last Answer : The ability of the polar carbonyl group to attract other polar molecules.

Description : Carbon dioxide is formed when to oxygen atoms chemically combined with a carbon atom which term best describes carbon dioxide?

Last Answer : Ggg

Description : The order of acidic strength of the hydrogen atom `(H_(alpha), H_(beta), H_(gamma))` in the given molecule is : `CH_(3)-underset(H_(beta))underset(|)(

Last Answer : The order of acidic strength of the hydrogen atom `(H_(alpha), H_(beta), H_(gamma))` in the given molecule ... D. `H_(beta)gt H_(alpha) gt H_(gamma)`

Description : A proton is identical to _____. (1) the nucleus of helium (2) the nucleus of a hydrogen atom (3) an alpha-particle (4) a beta particle

Last Answer : D. a beta particle

Description : The unwanted amino acids abstracted from the tissues are either used up by the tissue or in the liver converted into (A) Ammonia (B) Urea (C) Ammonium salts (D) Uric acid

Last Answer : Answer : B

Description : Which statement about the carbonyl group is NOT true? (a) The carbonyl carbon is sp2 hybridized. (b) The bond angles among the three atoms attached to the carbonyl carbon are 120°. (c) ... attached to the carbonyl carbon form a nonplanar geometry. (d) The carbonyl group forms resonance structures.

Last Answer : The three atoms attached to the carbonyl carbon form a nonplanar geometry

Description : What is the hybridization of the carbonyl oxygen in carboxylic acids? (a) sp (b) sp2 (c) sp3 (d) s-sp2

Last Answer : sp2

Description : Which of the following is not a correct statement about the electrophilic substitution mechanism of benzene? (a) Benzene functions as a nucleophile. (b) Formation of a carbocation intermediate is the ... hybridized carbon in the ring. (d) The addition product is a frequently observed minor product.

Last Answer : The addition product is a frequently observed minor product.

Description : In the addition of hydrogen bromide to alkynes, which of the following species is believed to be an intermediate? (a) vinyl anion (b) vinyl cation (c) vinyl radical (d) carbene

Last Answer : vinyl cation

Description : At physiological pH the ammonia is protonated to form

Last Answer : At physiological pH the ammonia is protonated to form

Description : What is the equation for the transmutation that occurs when an alpha particle combines with an oxygen-16 atom emitting a proton?

Last Answer : Need answer

Description : What is the hybridization and geometry of the carbonyl carbon in carboxylic acids and their derivatives? (a) sp3, tetrahedral (b) sp2, trigonal planar (c) sp2, tetrahedral (d) sp3, trigonal planar

Last Answer : sp2, trigonal planar

Description : Catenation is a property of the carbon atom which describes its ability to (a) bond with other carbon atoms (b) form double and triple bonds (c) exist in plant and animal form (d) form bonds in its ground state

Last Answer : bond with other carbon atoms

Description : Which nitrogen is protonated readily in the guanidine?

Last Answer : Which nitrogen is protonated readily in the guanidine? A. 1 B. 2 C. 3 D. none of the above