Alcohol acidity Q

[PremedicalS]

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Does methyl alcohol or ethyl alcohol have a lesser pKa (and thus stronger acid)?

I think the answer is that ethyl alcohol has a lesser pKa than methyl alcohol (so ethyl alcohol is a stronger acid than methyl alcohol) because the ethyl alkoxide is a weaker base than methyl alkoxide (because the longer alkyl chain can better handle the negative charge). Am I correct?

Thank you.

Also, can someone please explain the acidity trend for acid halides? Is HF << HCl < HBr < HI? How is this best explained? (For the respective bases, is F- > Cl- > Br- > I-....I- ? and is this trend in basicity of the anion best explained by size of the halide or electronegativity. Fluorine is most electronegative and smallest anion, so strongest base, whereas I is least electronegative and largest so can delocalize the negative charge best, so weakest).
- For acidity, is the bond length between H-I is greatest (and weakest) while H-F is smallest and strongest.

I also have a third question, can someone please explain the acidity trend within a period? Is water or HF a stronger acid. Likewise, is PH3 or SH2 a stronger acid? (Or should this be better stated PH4+ vs. SH3+?)

Just to double check...SH2 is a stronger acid than water, right?

Thanks in advance for your help.

 

[PremedicalS]

Also, is HClO or HF a weaker acid?

 

[Pose]

Methanol is more acidic than ethanol, because the additional carbon in ethanol (or it's bond, I guess) is electron donating. This has something to do with stability. I think if the alcohol is deprotonated, and therefore bears a negative charge, carbon isn't capable of stabilizing it.

 

[gwjib04]

Does methyl alcohol or ethyl alcohol have a lesser pKa (and thus stronger acid)?

I think the answer is that ethyl alcohol has a lesser pKa than methyl alcohol (so ethyl alcohol is a stronger acid than methyl alcohol) because the ethyl alkoxide is a weaker base than methyl alkoxide (because the longer alkyl chain can better handle the negative charge). Am I correct?

Thank you.

Also, can someone please explain the acidity trend for acid halides? Is HF << HCl < HBr < HI? How is this best explained? (For the respective bases, is F- > Cl- > Br- > I-....I- ? and is this trend in basicity of the anion best explained by size of the halide or electronegativity. Fluorine is most electronegative and smallest anion, so strongest base, whereas I is least electronegative and largest so can delocalize the negative charge best, so weakest).
- For acidity, is the bond length between H-I is greatest (and weakest) while H-F is smallest and strongest.

I also have a third question, can someone please explain the acidity trend within a period? Is water or HF a stronger acid. Likewise, is PH3 or SH2 a stronger acid? (Or should this be better stated PH4+ vs. SH3+?)

Just to double check...SH2 is a stronger acid than water, right?

Thanks in advance for your help.

As you go down the periodic table, atomic radius is increasing so the area the negative charge of the conjugate base can be spread is bigger. So the conjugate base is more stable as it gets bigger making the acid dissociation more favorable.

The exception to this is HF which is a weak acid. Its pKa is around 3. The pKa of water is 7. HF is stronger.

 

[Pose]

Another exception is with oxyacids.

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