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 : Phenol has smaller dipole moment than methanol. (OR) Why are dipole moments of phenols smaller than dipole moments of alcohols ?
Last Answer : Due to electron-withdrawing effect of the benzene ring, the C — O bond in phenol is less polar but in case of methanol due to electron-donating effect of — CH3 group, C — O bond is more polar.
Description : How an — OH group attached to carbon in the benzene ring activates benzene towards electrophilic substitution ?
Last Answer : The lone pair of electrons present on oxygen atom enter into resonance with the benzene ring. As a result, the electron density becomes higher at o- and p- position and due to higher electron density, the ring gets activated towards electrophilic substitution.
Description : Why is it that secondary alcohols can only undergo a single oxidation step in contrast to primary alcohols?
Last Answer : 1. Once the oxidation has reached the ketone stage, (primary alcohols on oxidation yield aldehyde where as secondary alcohols on oxidation yield a ketone), it is impossible to put more oxygen atoms on the relevant carbon atom without rupturing the backbone of the molecule.
Description : While separating a mixture of ortho and para-nitro phenols by steam distillation, name the isomer which will be steam volatile. Give reasons.
Last Answer : In o-nitrophenol, there is intramolecular hydrogen bonding as follows : In p-nitrophenol, there is intramolecular hydrogen bonding as follows : Due to intermolecular H ... -nitrophenol. Hence o-nitraphenol due to its lower b. p. is steam volatile while pnitrophenol is not.
Description : Alcohols acts as weak bases. Explain.
Last Answer : The oxygen atom of the hydroxyl group has two lone pairs of electrons. Therefore alcohols accept a proton from strong mineral acid to form oxonium ions. Hence act as weak bases.
Description : Di-tert butyl ether cannot be made by Williamson’s synthesis. Explain why ?
Last Answer : Ans. To prepare di tert-butyl ether by Williamson's synthesis, we need tert-butyl bromide and Sodium tertiary butoxide. Since tert-butyl bromide being 3°-alkyl halide prefers to ... rather than substitution, therefore the product obtained is isobutylene rather than ditertiary butyl ether.
Description : Ortho and paranitrophenols are more acidic than phanel. Draw the resonance structures of the corresponding phonoxide ion.
Last Answer : Ans:- Electronwithdrawal by nitro group makes the plenoxide ion more resonance stabilized and so the strength of phenel increases.
Description : Why phenol is acidic ?
Last Answer : Ans: In phenol dissociation takes place as follows. The conjugate base of phenol ie. Phenoxide ion is resonance stabilized. This is why the negative charge on oxygen atom is ... ion has less tendency to form undissociated phenol molecule and equilibrium lies towards right direction.
Description : Ethers are cleaved by acids not by based. Why ?
Last Answer : The C - O - C bond in ethers like the C - OH bond in alcohols is quite strong. In order to weaken it, the oxygen atom must be protonated. A subsequent nucleophile attack by a strong ... protonation of O atom of ether and therefore only acids can bring about the cleavage of ethers and not bases.
Description : Why are Grignard reagents soluble in ether but not in benzene ?
Last Answer : Ans. Grignard reagents from co-ordination complexes with ether but not benzene since the former has lone pair of electrons but the later does not.
Description : Name the products obtained when anisole is treated with HI.
Last Answer : Ans. Phenol and methyl iodide.
Description : What is usually added to ethyl alcohol to make it unfit for drinking purposes ?
Last Answer : Ans. Methanol and Pyridine.
Description : What is the main product obtained when vapours of t-butyl alcohol are passed over copper at 300° ?
Last Answer : Ans. Isobutylene (2-Methyl propene)
Description : Which group forms the strongest H-bonds to water molecules? (a) Alcohols (b) Ethers (c) Phenols (d) All equally strong
Last Answer : Phenols
Description : Phenols can be easily distinguished from alcohols because (a) phenols are soluble in NaOH, but alcohols are not (b) alcohols are soluble in NaOH, but phenols are not (c) phenols are soluble in NaHCO3, but alcohols are not (d) alcohols are soluble in NaHCO3, but phenols are not
Last Answer : phenols are soluble in NaOH, but alcohols are not
Description : Assertion : Phenols are more acidic than aliphatic alcohols. Reason : Phenoxides are stabilized by resonance.
Last Answer : Assertion : Phenols are more acidic than aliphatic alcohols. Reason : Phenoxides are stabilized by resonance. ... D. A is incorrect but R is correct
Description : Explain why nucleophilic substitution reactions are not very common in phenols.
Last Answer : Explain why nucleophilic substitution reactions are not very common in phenols.
Description : Which statement about the carbonyl group of ketones and aldehydes is true? I. It can attract nucleophiles. II. It can attract electrophiles. III. It tends to undergo addition reactions. IV. It tends to undergo substitution reactions. (a) I and III (b) II and IV (c) I, II, and III (d) I, III, and IV
Last Answer : I, II, and III
Description : Which of the following is not correct concerning substitution and elimination reactions of alkyl halides? (a) The electrophile replaces the leaving group. (b) Compounds containing electron-donating groups bonded to an ... replaced by another atom or group in substitution reactions. (d) (a) and (b)
Last Answer : (a) and (b)
Description : Esters can be formed by nucleophilic substitution reactions of : (a) carboxylic acids and alcohols ; acid-catalyzed (b) acid chlorides and alcohols (c) both of the above (d) neither of the above
Last Answer : both of the above
Description : Aldehydes undergo oxidation with KMnO4/H+ to give (a) Alcohols (b) Acetals (c) Ketones (d) Acids
Last Answer : Acids
Description : Benzene cannot undergo – (1) Substitution (2) Addition (3) Elimination (4) Oxidation
Last Answer : (3) Elimination Explanation: Benzene can not undergo Elimination reaction.
Description : Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?
Last Answer : Ans. Due to the presence of an electron cloud containing 6 pi electrons above and below the plane of the ring, benzene is a source of electrons. Consequently, it attracts ... . As a result, benzene undergoes electrophilic substitution reactions easily and nucleophilic substitution with difficulty.
Description : Which of the following will undergo substitution in the ortho and para positions rather than in the meta position? (a) Nitrobenzene (b) Benzoic acid (c) Acetanilide (d) Benzaldehyde
Last Answer : Acetanilide
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 : Alkyl halides undergo (a) Electrophilic substitution reactions (b) Electrophilic addition reactions (c) Nucleophilic substitution reactions (d) Nucleophilic addition reactions
Last Answer : Nucleophilic substitution reactions
Description : Benzene cannot undergo : (1) Substitution (2) Addition (3) Elimination (4) Oxidation
Last Answer : Elimination
Description : Which of the following can undergo nucleophilic substitution under ordinary conditions? I Allyl chloride II Benzyl chloride III n-Propyl chloride IV V
Last Answer : Which of the following can undergo nucleophilic substitution under ordinary conditions? I Allyl chloride II ... are correct D. I and III are correct
Description : Give reason: Alkanes undergo only substitution reactions but alkenes and alkynes undergo both substitution and addition reactions.
Last Answer : Alkenes and alkynes have double and triple bonds, which on breaking can add hydrogen atoms to satisfy the valency.
Description : `R-OH + HX to R -X + H_(2)O` In the above reaction the reactivity of different alcohols is
Last Answer : `R-OH + HX to R -X + H_(2)O` In the above reaction the reactivity of different alcohols is ... `gt` secondary D. Secondary `gt` primary `gt` tertiary
Description : How many isomers of `C_(5)H_(11)OH` will be primary alcohols?
Last Answer : How many isomers of `C_(5)H_(11)OH` will be primary alcohols? A. 5 B. 4 C. 2 D. 3
Description : Which one of the following compounds form zwitterions? (a) carbonyl compounds (b) amino acids (c) phenols (d) heterocyclic compounds
Last Answer : amino acids
Description : The greater acidity of carboxylic acids compared to alcohols arises primarily from : (a) the electron-donating effect of the hydroxyl group (b) the electron-withdrawing effect of the carboxyl ... of α-hydrogens of carboxylic acids (d) the resonance stability associated with the carboxylate ion
Last Answer : the resonance stability associated with the carboxylate ion
Description : Which of the following group of compounds is most soluble in water? w) alkanes (pron: ak-KANES) x) alcohols y) aldehydes (pron: al-deh-HIDES) z) alkenes (pron: al-KEENS)
Last Answer : ANSWER: X -- ALCOHOLS
Description : Acetyl chloride undergoes nucleophilic substitution at a faster rate than methyl acetate because __________. (a) the ester is more sterically hindered than the acid chloride (b) the acid chloride is ... is a better leaving group than chloride (d) chloride is a better leaving group than methoxide
Last Answer : chloride is a better leaving group than methoxide
Description : Phenols does not react with
Last Answer : Phenols does not react with A. sodium bicarbonate B. sodium hydroxide C. potassium hydroxide D. ferric chloride
Description : Assertion (A): Alkyl aryl ethers on reaction with HI give alkyl iodide phenols Reason (R): Aryl - oxygen bond is weaker than alkyl oxygen bond
Last Answer : Assertion (A): Alkyl aryl ethers on reaction with HI give alkyl iodide phenols Reason (R): Aryl - oxygen ... is false D. A is false but R is true
Description : The smell of fat turned rancid is due to (A) Presence of vit E (B) Presence of quinones (C) Phenols (D) Volatile fatty acids
Last Answer : Answer : D
Description : Protein is a polymer of (A) Sugars (B) Phenols (C) Amino acids (D) Carboxylic acids
Last Answer : Answer : C
Description : Phenols are added in gasoline to (A) Improve the octane number (B) Act as an antioxidant (C) Reduce its viscosity (D) Increase its pour point
Last Answer : (B) Act as an antioxidant
Description : Why are amines always less acidic than comparable alcohols?
Last Answer : Ans.--- Amines are less acidic than alcohols because of oxygen higher electronegative & smaller size. Therefore O-H breakes easily than N-H bond.
Description : Upon hydrolysis, proteins give (a) Amino acids (b) Hydroxy acids (c) Fatty acids (d) Alcohols
Last Answer : Amino acids
Description : Aliphatic primary amines react with cold nitrous acid to form (a) Alcohols (b) Diazonium salts (c) Nitriles (d) Nitroalkanes
Last Answer : Alcohols
Description : . Hunsdiecker reaction is used for the preparation of (a) Alkyl chlorides and bromides (b) Alkyl nitrates and nitrites (c) Ketenes (d) Alcohols
Last Answer : Alkyl chlorides and bromides
Description : Primary alcohols have boiling points that are _____________ the corresponding aldehydes. (a) Lower than (b) Higher than (c) About the same
Last Answer : Higher than
Description : Thiols are alcohol analogs in which the oxygen has been replaced by sulfur (e.g., CH3SH). Given the fact that the S-H bond is less polar than the O-H bond, which of the following ... (c) Hydrogen bonding forces would be the same. (d) No comparison can be made without additional information
Last Answer : Hydrogen bonding forces are weaker in thiols.
Description : Which of the following reagents can be used to oxidize 1° alcohols to aldehydes? (a) KMnO4 (b) MnO2 (c) K2Cr2O7 (d) PCC
Last Answer : PCC
Description : The acid-catalyzed dehydration mechanism for alcohols is best described as a(n) : (a) E1 . (b) E2 . (c) SN1 (d) SN2
Last Answer : E1 .
Description : Which of the following alcohols will give a yellow precipitate of iodoform with iodine and dilute NaOH solution? (a) 1-Propanol (b) 2-Propanol (c) 1-Butanol (d) 2-Methyl-2-propanol
Last Answer : 2-Propanol