Ca(OH)2, Sr(OH)2, Mg(OH)2, Ba(OH)2

Dibasic

Al(OH)3, Ga(OH)3, In(OH)3

Tribasic

What is the appropriate range of the acidity constant Ka?

Ranges from 10¹⁵ to 10^-60

The pKa of water is

15.74

A solution in which [H+] > [OH-] is ___ whereas a solution in which [H+] < [OH-] is ___.

- acidic

- basic

The pH of an acidic solution is ___ than ___ whereas for an alkine solution ___ than ___.

- lower than 7

- higher than 7

Identify the correct relationship

pH = -log[H3O+]

Arrange the following five compounds with the increasing order of acidity.

Increasing order:

The value of pH+pOH is equal to

14

Boron trifluoride-etherate can be considered as

Lewis acid-Lewis base complex

The transition metal salts, such as TiCl4, FeCl3, ZnCl2, and SnCl4, are

Lewis acids

A significant similarity between acetone, acetaldehyde, ethyl alcohol, acetic acid, acetyl chloride, and acetamide is all of these compounds are

Lewis base

The coordination of water with metal ions is a ___ acid-base reaction.

Lewis

The formation of hydronium ion is a ___ acid-base reaction.

Lewis

The interaction of Fe2+ in heme with O2 is a ___ acid-base reaction.

Lewis

Arrange the following acids according to decreasing order of acidity.

HI, HBr, HCl, HF (1 is most acidic and 4 is least acidic).

Arrange the following acids according to decreasing order of acidity.

1. Hypochlorous acid

2. Hypobromous acid

3. Hypoiodous acid

Why is CH3COOH a stronger acid than HOH?

In the case of water, the conjugate base hydroxyl anion (OH-) and resonance is not present because of the localized electron. But in acetic acid, resonance is present because of the delocalized electron. No free proton available in water but it's available in CH3COOH.

Arrange the relative strength of the following factors on acidity (structural effects) of a molecule.

1. Resonance

2. Atomic radius

3. Electronegativty

4. Inductive effect

Write the difference between the Inductive effect and the Field effect.

- Field effect = cloud of negative charge -> electron donation done through space.

- Inductive effect = electron donation through bond -> particle effect

Five +I groups

1. NH4

2. H3O+

3. C2H3+

4. CH3+

5. C3H5+

Five -I groups

1. NH2-

2. OH-

3. CHO-

4. NO2-

5. HSO3-

Benzoic acid is a stronger acid than acetic acid— explain.

Because of the -I effect of phenyl group.

The electromeric effect is seen in ___ pi system, whereas the resonance effect predominates in ___ pi system.

- unconjugated

- conjugated

Hyperconjugation is also known as no ___ resonance.

bond

The IUPAC name of Isobutane is ___.

2-Methylpropane

The compounds n-Butane and Isobutane are ___ isomers, whereas Ethyl alcohol and Dimethyl ether are ___ isomers.

- skeletal

- functional

Isopropylamine and Propylamine are ___ isomers.

positional

The H-H (eclipsed) torsional strain is ___ kj/mol, whereas the H-CH3 (eclipsed) torsional strain is ___ kj/mol.

- 4

- 6

The CHE-CH3 (eclipsed) torsional strain is ___ kj/mol whereas the CH3-CH3 (gauche) torsional strain is ___ kj/mol.

- 7

- 0

According to Baeyer's Strain Theory, the angle strain in cyclopropane is ___ whereas that of cyclobutane is ___.

- 49

- 19

According to Baeyer's Strain Theory, the angle strain in cyclopentane is ___ whereas that of cyclohexane is ___.

- 1

- -11

Why was Baeyer' theory incorrect?

Because he said that cycloalkanes are planar when they're not and he didn't consider torsional strain.

In cyclopropane, all C-H bonds are ___.

eclipsed

In cyclobutane, the bend ___ angle strain but ___ torsional strain.

- increases

- decreases

The ___ ring looks like an envelope.

cyclopentane

What do you mean by the flipping of a cyclohexane ring?

The exchange of axial and equatorial positions because chair conformations readily interconnect.

Because of the flipping of a cyclohexane ring, the ___ hydrogens become ___ and the ___ rings become ___.

- axial hydrogens become equatorial

- equatorial hydrogens become axial

In general, equatorial positions give more ___ isomer.

stable

What is the dihedral angle between Ha and Hb?

60°, gauche

Consider this chair conformation. When the ring flips...

the chlorine becomes equatorial, and the ethyls become axial.

The compounds represented by the structures are

cis-trans isomers

Is the following compound more or less acidic than phenol?

Here, resonance decreases basicity of the phenol, increasing the acidity.

Compare CF3SO3H and CH3SO3H, which has the higher pka? Why?

CH3SO3H has a higher pka than CF3SO3H. The F is more electronegative making the molecule more acidic with a lower pka.

Explain with appropriate equations why water is called amphoteric?

Water is both a Bronsted base (accepts proton) and Bronsted acid (donates proton).

- Base: H2O + HCl -> H3O+ +Cl-

- Acid: H2O + NH3 -> OH- + NH4

What do you mean by conjugate acid and conjugate base?

Acid loses proton to form a conjugate base and base accepts proton to form conjugate acid.

The aqueous solution of ammonium chloride (NH4Cl) is acidic, whereas the aqueous solution of sodium cyanide (NaCN) is basic. Justify.

Ammonium chloride is a salt of a weak base and strong acid. It undergoes salt hydrolysis to produce an acidic solution whereas sodium chloride is a salt of a strong acid and strong base it doesn't undergo salt hydrolysis so it remains basic.

NH3 + HCl -> NH4Cl

NH4Cl hydrolysis to produce H+ ion so NH4Cl is acidic.

NaCN -> Na+ + CN- (strong acid)

CN- + H2O -> HCN + OH- (produce OH- making it a base)

Besides proton, Bronsted acids are not Lewis acids. Justify.

Bronsted acids give away a proton while Lewis acids accept an electron pair. Bronsted acids are not Lewis acids because they can't accept an electron pair directly.

Aluminum hydroxide (Al(OH)3) is amphoteric in nature. Justify.

When it's a solid, it can react with a strong base to form complex compound so it behave like a Lewis acid. Accepts electron pair.

Al(OH)3 + OH- -> Al(OH)4

In Al(OH)3 + 3H+ -> Al3+ + 3H2O, aluminum trihydroxide reacts with proton and you get tri positive aluminum and water is formed so here aluminum trihydroxide is a Bronsted base. Accepts proton.

Al(OH)3 is a Bronsted base but Lewis acid. Explain.

It's a Bronsted base because in Al(OH)3 + 3H+ -> Al3+ + 3H2O it accepts a proton.

It's a Lewis acid because in Al(OH)3 + OH- -> Al(OH)4 it accepts an electron pair.

HI is more acidic than HF. Explain.

The atomic radius of H-I is bigger than of H-F. As size increases, acidity increases.

Arrange the following molecules according to increasing acidic order.

1. Methane

2. Ammonia

3. Water

4. Hydrofluoric acid

This is based on electronegativity. The more electronegative, the stronger the acid.

How can you explain the acid strength of Hypochlorous acid, Chlorous acid, and Perchloric acid?

This is based on the oxidation number which focuses on the number of bonds.

1. Hypochlorous acid (weakest)

2. Chlorous acid

3. Chloric acid

4. Perchloric acid (strongest)

Arrange and justify the order of acidic strength of the following compounds.

1. Butanoic acid

2. 4-Chlorobutanoic acid

3. 3-Chlorobutanoic acid

4. Chlorobutanoic acid

The closer Cl gets to COOH, the stronger the acid. By adding an electron withdrawing group, you stabilize the conjugate base resulting in a strong acid. The magnitude of the inductive effect depends on the number of bonds between the electron withdrawing group and the size of the negative charge.

Arrange and justify the order of acidic strength of the following compounds.

1. Chloroacetic acid

2. Fluoroacetic acid

3. Dichloroacetic acid

4. Trichloroacetic acid

Stronger e-w groups stabilize the anion of the conjugate base more than weaker groups, leading to stronger acids. F is more electronegative and stronger withdrawing group than Cl. However, multiple e-w groups increase the acidity more than a single group since they pull the electron density, making dichloroacetic acid a stronger acid than trichloroacetic acid.

Methanesulfonic acid (pka = -1.2) os stronger acid than acetic acid (pka = 4.74). Explain.

The acetate ion has negative charge shared by 2 oxygen atoms while the methanesulfurate ion has the negative charge spread over 3 oxygen atoms; this delocalization helps stabilize the anion. The pka acids of the original acids corresponding to the anions show that acids are stronger if they lose a proton to give resonance-stabilized conjugate bases.

What do you mean by the resonance effect? Arrange the following species according to increasing inductive effect.

The flow of electrons from one part of a conjugated pi system to the other caused by phenomenon of resonance. The polarity induced in a molecule by the reaction between a lone pair of electrons and a pi bond.

-CH3 < -C2H5 < (CH3)2OH < (CH3)3C

Ethyl carbocation is less stable than tert-Butyl carbocation. Explain.

Based on the inductive effect, more alkyl groups are donating e- along the sigma bonds towards the charged carbon so it's more stable. This is not observed in ethyl carbocation so it's less stable.

Arrange and justify the order of acid strength of the following molecules.

1. ICH2COOH

2. BrCH2COOH

3. CICH2COOH

4. FCH2COOH

5. O2NCH2COOH (stronger)

6. CH3COOH

1. The atoms are present in any cycloalkane molecule lie in same plane and thus all cycloalkanes are co-planar. Carbon-Carbon angle is 109°28'.

2. The deviation of bond angle from the normal tetrahedral angle is called angle strain.

3. The greater the angle strain, the greater is the stability of ring.

4. The higher the stability of the ring, the greater would be its easy of formation.

Postulates of Baeyer's strain theory

Angle strain

Expansion or compression of bond angles away from the preferred 109.5°

Torsional strain

Eclipsing of bonds on neighboring atoms (from electron pair repulsion, negative charges repel each other so torsional strain).

Steric strain

Repulsive interactions between nonbonded atoms in close proximity (big groups hit each other)