Superacids and Superbases
Summary
TLDRThe 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
🧪 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).
🔬 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.
Mindmap
Keywords
💡Hydronium Ion
💡Aqueous Solution
💡Super Acids
💡Hammett Function (H0)
💡Pure Acid Solutions
💡Fluorosulfonic Acid
💡Magic Acid
💡Hydrogen Fluoride (HF)
💡Super Bases
💡Hydroxide Ion
💡Proton Transfer
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
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