Reasoning Based Questions
Haloalkanes and Haloarenes:
- Sulphuric acid is not used during the reaction of alcohols with KI.
- Alkyl halides are generally not prepared in laboratory by free radical halogenations of alkanes.
- The boiling points of alkyl halides decrease in the order: RI > RBr > RCl > RF.
- Haloalkanes have higher boiling points as compared to those of corresponding alkanes.
- The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.
- Alkyl halides, though polar, are immiscible with water.
- Grignard reagents should be prepared under anhydrous conditions.
- Aryl halides are extremely less reactive towards Nucleophilic Substitution reactions.
- p – nitro chlorobenzene undergoes nucleophilic substitution faster than chlorobenzene
- The treatment of alkyl chlorides with aq.KOH leads to the formation of alcohols but in the presence of alc.KOH alkenes are major products.
- Haloalkanes react with KCN to form alkyl cyanides as main product while AgCN forms isocyanides as main product.
- Allyl chloride is more reactive than n – propyl chloride towards nucleophilic substitution reaction.
- P-Dichlorobenzene has higher m.p and solubility than those of o- and m- isomers.
- Chloroform is stored in closed dark coloured bottles.
- Although chlorine is an electron withdrawing group, yet it is ortho-, para– directing in electrophilic aromatic substitution reactions.
ALCOHOLS, PHENOLS & ETHERS:
- Phenols not undergo Nucleophilic substitution reaction easily but undergo elecrophilic substitution reaction easily at ortho and para positions.
- In Phenol, the –OH group activates the benzene ring towards elecrophilic substitution and directs the substituents to Ortho and para positions in benzene ring.
- The –OH group in phenols is more strongly held as compared to –OH group in alcohols.
- Phenol does not undergo protonation easily.
- Nitration is an example of aromatic electrophonic substitution and its rate depends upon the group already present in the benzene ring.Out of benzene and phenol which one is more easily nitrated and why?
- The carbon –oxygen bond in phenol is slightly stronger than in methanol
- In Kolbe’s reaction instead of phenol phenoxide ion is treated with carbon dioxide.why
- Phenol is more acidic than alcohols(Ethanol)
- The presence of electron withdrawing groups such as nitro group enhances the acidic strength of phenol.
- The presence of electron releasing groups such as alkyl group decreases the acidic strength of phenol.
- Ortho – nitrophenol is more acidic than Ortho – methoxyphenol.
- Out of 2-Chloroethanol & ethanol which is more acidic & why?
- The acid strength of alcohols decreases in the following order:1o>2o>3o.
- Arrange the following compounds in increasing order of acidity and give a suitable explanation. Phenol, o-nitrophenol,o-cresol
- Arrange the following compounds in increasing order of acidity and give a suitable explanation.Phenol,water & Alcohol.
- Out of o-nitrophenol & o-cresol which is more acidic & why
- Arrange the following compounds in increasing order of acidity H2O,ROH.CHCH.
- Phenol has small dipole moment than methanol.
- O-nitrophenol has lower boiling point than p-nitrophenol
- Out of o-nitrophenol & p-nitrophenol which is more volatile & why
- O-nitrophenol is steam volatile whereas p-nitrophenol is not.
- Alcohols are comparatively more soluble in water than the corresponding hydrocarbons
- Propanol has higher boiling point than that of the hydrocarbon, butane.
- Lower alcohols are soluble in water, higher alcohols are not.
- The boiling point of alcohols and phenols increase with increase in number of carbon atoms.
- In alcohols the boiling point decreases with increase in branching.
- The boiling point of alcohols & phenols are higher in comparison to hydrocarbons, ethers, haloalkanes.
- Thionyl chloride preferred over PCl5 in nucleophilic substitution Rxn to convert alcohol to alkyl halide.
- Among HI, HBr, HCl, HI is most reactive towards alcohol.
- Out of ethanol and propanol, ethanol gives iodoform test whereas propanol does not do so.
- The reactivity of all the three classes of alcohols with Lucas reagent is different.
- In aryl alkyl ethers (i) the alkoxy group activates thebenzene ring towards electrophilic substitution and (ii) it directs the incoming substituents to ortho and para positions in benzene ring..
- Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method.
- O=C=O is nonpolar while R-O-R is polar.
- Ethers can be prepared by Williamson synthesis in which alkyl halide is reacted with sodium alkoxide.Di-tert butyl ether can’t be prepared by this method.why
- Aldehydes are more reactive than Ketones towards Nucleophilic addition reaction
- Cyclohexanone forms cyanohydrin in good yield but 2,2,6 – tri methylcyclohexanone does not.
- Arrange the following compounds in increasing order of their reactivity in nucleophilic addition reactions.with reasons
(i) Ethanal, Propanal, Propanone, Butanone.
(ii) Benzaldehyde, p-Tolualdehyde, p-Nitrobenzaldehyde, Acetophenone.
(iii) Acetaldehyde, Acetone, Di-tert-butyl ketone, Methyl tert-butyl ketone
- Would you expect benzaldehyde to be more reactive or less reactive in nucleophilic addition reactions than propanal.
- Aldehydes and Ketones have lower boiling point than alcohols.
- The boiling points of aldehydes and ketones are higher than hydrocarbons and ethers of comparable molecular masses.
- Why is there a large difference in the boiling points of butanal and butan-1-ol?
- The lower members of aldehydes and ketones such as methanal,ethanal and propanone are miscible with water in all proportions.
- There are two – NH2 group in semi carbazide however only one is involved in the formation of semi carbazones.
- It is necessary to control the pH during the reaction of aldehydes and ketones with ammonia derivatives.
- o-hydroxybenzaldehyde is a liquid at room temperature while p-hydroxybenzaldehyde is a high melting solid.
- Formaldehyde does not take part in Aldol condensation.
- Benzaldehyde gives a positive test with Tollens reagent but not with Fehling and Benedict’s solution.
- Carboxylic acids are more acidic than phenols.
- Carboxylic acids are more acidic than alcohols or phenols although all of them have hydrogen atom attached to a oxygen atom (—O—H)
- Electron withdrawing groups increase the acidity of carboxylic acids.
- Electron donating groups decrease the acidity of carboxylic acids.
- Formic acid is stronger acid than acetic acid
- Chloroacetic acid is stronger than acetic acid.
- Arrange the following compounds in increasing order of acid strength
(i) CH3CH2OH, CH3COOH, ClCH2COOH, FCH2COOH, C6H5CH2COOH
(ii) C6H5COOH, FCH2COOH, NO2CH2COOH
(iii) CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOH, (CH3)2CHCOOH,CH3CH2CH2COOH
(iv) Benzoic acid, 4-Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4-Methoxybenzoic acid
- Which acid of each pair shown here would you expect to be stronger?(i) CH3CO2H or CH2FCO2H (ii) CH2FCO2H or CH2ClCO2H(iii) CH2FCH2CH2CO2H or CH3CHFCH2CO2H. .
- Carboxylic acids are higher boiling liquids than aldehydes, ketones and even alcohols of comparable molecular masses.
- Aliphatic carboxylic acids having upto four carbon atoms are miscible in water
- During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the water or the ester should be removed as fast as it is formed.
- HCOOH does not give HVZ (Hell Volhard Zelinsky) reaction but CH3COOH does.
- Carboxyl group in benzoic acid is meta directing
- Melting Point of an acid with even number of carbon atoms higher than those of its neighbours with odd number of carbon atoms
- Carboxylic acids do not give the characteristic reactions of carbonyl group.
- Carboxylic acids contain carbonyl group but do not show the nucleophilic addition reaction like aldehydes or ketones.
- Amines are less acidic than alcohols of comparable molecular masses.
- Primary amines have higher boiling point than tertiary amines?
- Aromatic primary amines cannot be prepared by Gabriel phthalimide synthesis?
- Gabriel phthalimide synthesis is preferred for synthesising primary amines.
- Ethylamine is soluble in water whereas aniline is not.
- Aniline is soluble in aqueous HCl?
- Methylamine in water reacts with ferric chloride to precipitate hydrated ferric oxide.
- Although amino group is o– and p– directing in aromatic electrophilic substitution reactions, aniline on nitration gives a substantial amount of m-nitroaniline.
- Direct nitration of aniline is not carried out. Explain why?
- NH2 group of aniline acetylated is before carrying out nitration?
- Aniline does not undergo Friedel-Crafts reaction.
- Benzene diazonium chloride is not stored and is used immediately after its preparation?
- Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
- The presence of a base is needed in the ammonolysis of alkyl halides.
- The observed Kb order Et2 NH Et3N EtNH2in aqueous solution .where Et is ethyl
- Aliphatic amines are stronger bases than aromatic amines?
- MeNH2 is stronger base than MeOH?
- pKb of aniline is more than that of methylamine.