Alcohols Flashcards
Write out the combustion equation for alcohols: CxHyOH
CxHyOH + (x+y/4 -1/4)O2 —> xCO2 + (Y/2+1/2) H2O
What is the general formula for alcohols?
CnH2n+1OH
Why are alcohols weaker acids than water?
Electron donating alkyl groups on alcohol intensifies negative charge on the oxygen atom of the conjugate base, RO-, destabilising it to a greater extent. Hence, RO- is less stable than OH-, and will have a smaller extent of dissociation. It is thus a weaker acid than water.
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The bulky alkyl group interferes with the formation of ion-dipole interactions between water molecules and the alkoxide ion, leading to a lower degree of stabilisation of the anion.
What is the difference between acid base reactions that alcohols and phenols can undergo?
Alcohols do not react with bases such as NaOH, only reacts with Na in an acid metal displacement reaction.
Phenols can undergo acid base reaction with NaOH as it is a stronger acid than alcohols. Phenols can undergo acid-metal displacement with Na as well.
Why must add NaOH to phenol and acyl chloride condensation reaction
In condensation reaction, phenol acts as nucleophile, attacking electron deficient carbon in acyl chloride.
A: Phenol is a weak nucleophile as the lone pair of electrons on O can delocalise into the benzene ring, making the lone pair of electrons less available for condensation reaction. Phenoxide ion must first be produced via AB reaction to generate a stronger nucleophile.
Why are phenols stronger acids than water?
P orbital of oxygen overlaps with the pi electron cloud of the benzene ring.
Negative charge on oxygen is able to delocalise into benzene ring, thus reducing the intensity of the negative charge. Hence conjugate base of phenol is more stable than that of water and phenol is a stronger acid
What is a chemical test for phenol?
Add Neutral FeCl3 solution. A violet complex is observed
