Superacids and Superbases

Summary

The video script delves into the concept of acidity, explaining that in aqueous solutions, the hydronium ion represents the strongest acid. It discusses the transition to non-aqueous solutions and the use of the Hammett function (H0) to measure acidity beyond the pH scale. The script introduces super acids like fluorosulfonic acid and mixtures involving HF and SbF5, which can even protonate hydrocarbons. It also touches on super bases, such as lithium amide, and their reactivity with water, emphasizing that these substances operate in anhydrous conditions.

Takeaways

• 🌡️ The strongest acid in water is the hydronium ion, and no stronger acid can override its strength in an aqueous solution.
• 🔄 To achieve higher acidity, one must move from equal solutions to other solvents, such as pure acid solutions, which can be referred to as super acids.
• 📊 For non-aqueous solutions, the Hammett function (H0) is used instead of pH to measure the strength of acids and bases beyond the usual pH scale of 0 to 14.
• 🚫 Pure sulfuric acid has a relative strength, not a pH of minus 12, indicating an extremely strong acid that cannot be represented by a simple hydrogen ion concentration.
• 🔝 Adding more SO3 to sulfuric acid can create H2S2O7, which has a Hammett function of minus 15, showing an increase in acidity.
• 🧪 Replacing an oxygen in sulfuric acid with fluorine results in fluorosulfonic acid, which has a Hammett function of minus 15.1, indicating a slight increase in acidity.
• 🌐 Even weak acids like hydrogen fluoride can become super acids when in their pure liquid state, forming the H2F cation.
• 🔬 The addition of antimony pentafluoride (SbF5) to solutions can further increase their acidity, such as in the case of chlorosulfonic acid plus SbF5, which has a Hammett function of minus 19.
• ✨ The strongest known acid is a mixture of HF and SbF5, which can protonate hydrocarbons, including methane, which normally has no acidic properties.
• 🔄 In the absence of water, super bases like lithium amide can be stronger than hydroxide, but they react instantly with water to form hydroxide ions.
• 🧪 Nitric acid in sulfuric acid forms NO2+ and H3O+ cations, which are important in organic chemistry for protonation reactions.

Q & A

What is the strongest acid in water?

The strongest acid in water is the hydronium ion (H3O+). No matter what stronger acid is added, it will instantly become hydronium ion and the corresponding anion in the aqueous solution.

Can the strength of hydronium ion be overridden by other acids?

No, the strength of the hydronium ion cannot be overridden by other acids in an aqueous solution.

How can we achieve higher acidity than that of hydronium ion?

To achieve higher acidity, one must use pure acid solutions instead of aqueous solutions and consider super acids.

What are super acids and how are they different from regular acids?

Super acids are acids that are stronger than 100% sulfuric acid. They are capable of protonating hydrocarbons and are measured using the Hammett function (H0) instead of pH.

What is the Hammett function (H0) and how is it used?

The Hammett function (H0) is a scale used to measure the acidity of non-aqueous solutions, extending beyond the usual pH range of 0 to 14.

What is the pH of pure sulfuric acid?

The pH of pure sulfuric acid is not accurately represented by the pH scale; instead, it is described as having a relative strength of minus 12, indicating its extreme acidity.

How does the addition of SO3 affect the acidity of sulfuric acid?

Adding more SO3 to sulfuric acid can form H2S2O7, which has a Hammett function of minus 15, indicating an even stronger acidity.

What is fluorosulfonic acid and how strong is it?

Fluorosulfonic acid is a super acid with a Hammett function of minus 15.1, indicating it is one of the strongest acids known.

Why can weak acids like hydrogen fluoride become stronger in the absence of water?

In the absence of water, weak acids like hydrogen fluoride can form cations such as H2F+, which are much stronger than the hydronium ion, making the acid significantly stronger.

What is 'magic acid' and why is it called so?

Magic acid is a mixture of chlorosulfonic acid and antimony pentafluoride (SbF5) with a Hammett function of minus 19. It is called 'magic' because it can protonate hydrocarbons, including a candle, which dissolves when accidentally placed in the solution.

What is the strongest acid known today?

The strongest acid known today is a mixture of hydrogen fluoride (HF) and antimony pentafluoride (SbF5), which can protonate even methane, a molecule with no available lone pair electrons for protonation.

How do super bases differ from regular bases in water?

Super bases, such as lithium amide, are much stronger than regular bases like hydroxide ions in water. They are typically used in the absence of water to avoid immediate reaction with it to form hydroxide ions.

What happens when super acids and super bases react with water?

Super acids and super bases react instantaneously with water to form hydroxide ions (OH-) and hydronium ions (H3O+), respectively.

Why is the geometry of the protonated methane molecule complex?

The geometry of protonated methane is complex because one of the hydrogen atoms is connected to two other hydrogen atoms, leading to a structure that could be described as having symmetry between D3h or C4v.

What is the significance of the reaction between nitric acid and sulfuric acid in organic chemistry?

The reaction between nitric acid and sulfuric acid is significant because it forms NO2+ and H3O+ cations, which are important in organic chemistry for their ability to act as strong proton donors.

Outlines

00:00

🧪 Super Acids and Their Properties

This paragraph discusses the concept of acidity in aqueous solutions, highlighting that the strongest acid in water is the hydronium ion. It explains that while you cannot surpass the strength of hydronium, you can achieve higher acidity by using pure acid solutions, which are referred to as super acids. The paragraph also introduces the Hammett function (H0) as a measure of acidity beyond the pH scale, providing examples of super acids like fluorosulfonic acid and magic acid, which are capable of protonating hydrocarbons. The narrative further explores the transformation of weak acids into super acids when water is removed, and the creation of even stronger acidic solutions with the addition of antimony pentafluoride (SbF5).

05:02

🔬 Super Bases and Their Reactions

The second paragraph delves into the topic of super bases, contrasting them with the hydroxide ion as the strongest base in water. It outlines the need to eliminate water to achieve stronger bases, such as potassium hydride and sodium amide, and introduces lithium amide as an exceptionally strong base. The paragraph also touches on the reactivity of super acids and super bases with water, emphasizing that their effects are only observable in the complete absence of water. Additionally, it discusses the importance of protonation reactions involving super acids in organic chemistry and the formation of cationic species like NO2+ in the presence of nitric acid and sulfuric acid.

Keywords

💡Hydronium Ion

Hydronium ion is a key concept in the video script, referring to the ion formed when acids dissolve in water. It is represented as H3O+. The video explains that regardless of the strength of the acid added to water, the solution will predominantly contain hydronium ions, making it impossible to exceed the acidity of hydronium. This concept is central to understanding the limitations of acidity in aqueous solutions.

💡Aqueous Solution

An aqueous solution is a solution in which the solvent is water. In the context of the video, it is mentioned that when acids are added to water, they form hydronium ions, making the solution acidic. The script emphasizes that the acidity of an aqueous solution is inherently limited by the formation of hydronium ions, which is a fundamental aspect of understanding acid behavior in water.

💡Super Acids

Super acids are a class of acids that are stronger than common strong acids like sulfuric acid. The script mentions that to achieve higher acidity than that of hydronium ions, one must use non-aqueous solvents or pure acid solutions. Examples given in the video include fluorosulfonic acid and magic acid, which are known for their extreme acidity and ability to protonate hydrocarbons.

💡Hammett Function (H0)

The Hammett function, denoted as H0, is a measure of acidity in non-aqueous solutions. The video script explains that when dealing with non-aqueous solutions, the pH scale is not applicable, and the H0 scale is used instead. This function extends the pH scale beyond its usual range of 0 to 14, allowing for the measurement of super acids like fluorosulfonic acid.

💡Pure Acid Solutions

In the context of the video, pure acid solutions refer to solutions that are not diluted with water. The script discusses how moving from equal solutions to pure acid solutions can increase acidity. This is exemplified by the transition from a 1 M sulfuric acid solution to pure sulfuric acid, which has an H0 value of -12, indicating its extreme acidity.

💡Fluorosulfonic Acid

Fluorosulfonic acid is highlighted in the script as a super acid with an H0 value of -15.1. It is formed by replacing one oxygen in sulfuric acid with fluorine. The video explains that this acid is so strong that it can protonate hydrocarbons, demonstrating the concept of super acidity beyond the limits of aqueous solutions.

💡Magic Acid

Magic acid, a mixture of chlorosulfonic acid and antimony pentafluoride (SbF5), is described in the video as an extremely strong acid with an H0 value of -19. It is noted for its ability to protonate hydrocarbons, including methane, which is typically very resistant to protonation. The script uses the anecdote of a candle dissolving in magic acid to illustrate its exceptional strength.

💡Hydrogen Fluoride (HF)

Hydrogen fluoride is mentioned in the script as a weak acid in its pure liquid form but becomes a super acid when it forms H2F+ cations. The video explains that the removal of water allows even weak acids like HF to exhibit strong acidity, highlighting the role of the solvent in determining acid strength.

💡Super Bases

Super bases are bases that are stronger than common strong bases like sodium hydroxide. The script discusses how to achieve super basicity by moving away from aqueous solutions. Examples provided include lithium amide, which is described as a fantastically strong base, capable of reacting instantaneously with water to form hydroxide ions.

💡Hydroxide Ion

The hydroxide ion, represented as OH-, is the ion formed when bases dissolve in water. The video script explains that in aqueous solutions, the hydroxide ion is the strongest base. However, to achieve super basicity, the script suggests moving to non-aqueous solvents, which allows for the formation of stronger bases.

💡Proton Transfer

Proton transfer is a fundamental chemical reaction where a hydrogen ion (proton) is transferred from one molecule to another. The video script uses the example of magic acid protonating hydrocarbons to illustrate this concept. It is a key mechanism in acid-base chemistry, explaining how super acids can react with even non-reactive molecules like methane.

Highlights

The strongest acid in water is the hydronium ion, which cannot be overridden in strength.

To achieve higher acidity, one must use pure acid solutions in non-aqueous solvents.

Super acids are extremely strong acids, named for their ability to surpass the acidity of hydronium ions.

The Hammett function H0 is used to measure acidity in non-aqueous solutions, extending beyond the pH scale.

Pure sulfuric acid has a relative strength of minus 12, indicating its extreme acidity.

Adding more SO3 to sulfuric acid results in H2S2O7, with a Hammett function of minus 15.

Fluorosulfonic acid has a Hammett function of minus 15.1, making it a very strong acid.

Weak acids like hydrogen fluoride become super acids in their pure liquid state.

The addition of antimony pentafluoride (SbF5) to acid solutions significantly increases their acidity.

Chlorosulfonic acid mixed with SbF5 has a Hammett function of minus 19, capable of protonating hydrocarbons.

The strongest known acid is a mixture of HF and SbF5, with a complex cationic structure.

Super acids can protonate even methane, which has no lone pairs of electrons, challenging traditional rules.

The geometry of protonated methane involves a connection to two hydrogen atoms, suggesting a unique structure.

Protonated hydrocarbons are important in oil processing, as seen with nitric acid in sulfuric acid forming NO2+ and H3O+.

Super bases, such as lithium amide, are stronger than hydroxide and react instantaneously with water.

The strength of bases in water is limited by the presence of water, necessitating their use in anhydrous conditions.

Super acids and super bases are only stable and effective in the complete absence of water, even in trace amounts.

Transcripts

the strongest acid

in water is hydronium ion

whatever stronger acid you put in

aqueous solution it will instantly

become

hydronium ion and

anion of that compound you put

you cannot override strength of

hydronium

but if you want to go

to higher acidity

can we do something yes we can we just

need to go from equal

solutions to other solvents

the best approach is to go to pure acid

solutions

and some of these assets are so strong

that we name them super acids

same is true for bases

when you are coming from

water to non-aqueous solutions

you need to use so-called hammett

function

h0 instead of ph

which is continuation of ph

scale out of usual range

0 to 14.

so if you take pure

sulfuric acid

you will have ph

of minus 12 no this is not ph

you cannot have h plus concentration

10 power 12. this is relative strength

of acid

so you are moving in acidity

same way as you are moving from diluted

sodium hydroxide to h plus

and then the same jump in acidity from

one molar sulfuric acid to

pure sulfuric acid

if you add more so3 you'll have

h2s2 or 7

which will have hammered function of

minus 15.

if you remove one of

oxygens and replace it with fluorine

you will have fluorosulfonic acid

with hermit function minus 15.1

now it's interesting when you remove

water

even weak acids can become

stronger like hydrogen fluoride which is

weak acid when it is pure

liquid is becoming fantastically strong

super acid and the reason is such an

equation

three molecules of hf giving us

h2f cation not hydronium

but h2f you see it's somehow

similar to hydronium and h

f2 minus ni plural

triplic acid so

cf3 and sulfuric

is also very strong in pure state

now addition of antimony penta fluoride

sbf5 makes these

solutions even stronger acidic

so chlorosulfonic

acid plus sbf5

has hammered function of minus 19.

it's so strong it can protonate

hydrocarbons

so it was named magic

acid because when the candle on

christmas was put

accidentally in solution of it it just

dissolved

being protonated the strongest

acid we know for today is

mixture of hf and

sbf5

so there is catine of this sort

and anion such type in fact it's more

complex you have

chain of sb

f5 units connected

through f2 minus like here

and you have catin like that

h2f plus

what these acids can do they can

protonate hydrocarbons

even methane which is

absolutely again the rules you have five

bonds to methane

but in fact there are

four of them one is connected to two

hydrogen

atoms what's geometry of this molecule

uh it's something like only move like

this

cartoon you have something between d3h

or c4v or even this

another very common protonation reaction

she may involve

different hydrocarbons so

it's very important in oil processing

nitric acid when it's

put in sulfuric acid makes no2 plus

cation

and h3o plus so you have one more

cationic species that is fantastically

important in organic chemistry

same story happens with

basis when you

have basic solution in

water strongest base is hydroxide

eye phosphate is weaker

cyanide even weaker ammonia and

hydrazine

are relatively weak bases can we go

with stronger base and hydroxide yes

but we need to get rid of water

so example of super

bases are potassium hydride and

sodium geometries

but this is not strong enough such a

molecule

as lithium amide of this structure

as fantastically strong base

of course super acids and super bases

instantaneously react with water

making hydroxide and hydronium

so all these works only in complete

absence even of traces of water