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Organic Chemistry

Cool goIITian

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30 Jun 2008 23:17:21 IST

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which is more basic ? CH3O- (methoxide ion) or OH- (hydroxyl ion)

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which is more basic ? CH3O- (methoxide ion) or OH- (hydroxyl ion)

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Tarin Bansal

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30 Jun 2008 23:23:41 IST

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CH3OH is more acidic than water. Means its conjugate base wud be less basic than water's.

So, basicity order is ---> OH- > CH3O-

biswarup

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1 Jul 2008 00:41:24 IST

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OCH3 is more basic due to the +ieffect of CH3 which is missing in OH.

Gaurav Sood

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1 Jul 2008 11:44:55 IST

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due to +i effect of ch3, electron density will increase on O and hence, will be more basic...

Tarin Bansal

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1 Jul 2008 16:25:14 IST

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Logically both of u r correct but chemistry is an experimental science and logic cant challenge experimental observations.

Pka of CH₃OH = 15.5

PKa of H₂O = 15.7

Means methanol is more acidic than water. Means its conjugate base wud be less basic than water's.

Hence basicity order will be--->

OH^- > CH₃O^-

Saurabh Sood

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2 Jul 2008 11:37:42 IST

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i agree with tarin's answer. OH- is a stronger base, but from what i know, alcohols are less acidic than water.

Quoting from Wikipedia :

Alcohols, like water, can show either acidic or basic properties at the O-H group. With a pKa of around 16-19 they are generally slightly weaker acids than water, but they are still able to react with strong bases such as sodium hydride or reactive metals such as sodium. The salts that result are called alkoxides, with the general formula RO- M+.

pka of water : 15.7
pka of methanol : 15.5

so methanol is more acidic than water, but then it contradicts what i have quoted above.

Gaurav Sood

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2 Jul 2008 13:09:31 IST

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if its the experimental data, then u'r definately right...

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