C15. Alcohols Flashcards
What is the general formula for alcohol?
CnH2n+1OH
What’s the functional group of alcohols?
Hydroxyl group - OH
Why do alcohols have relatively high melting and boiling points?
Hydrogen bond intermolecular force, between molecules
What happens to the alcohols melting and boiling points as Mr increases?
Boiling and melting point increase
What are the properties of alcohols?
Low volatility; High melting and boiling point; Soluble in water (first 3 alcohols)
What is volatility?
How readily a substance evaporates
Why are alcohols soluble in water and why are some not?
hydrogen bonds form between hydroxyl group of alcohol and polar OH groups of water; Solubility decreases as chain increases, large part of alcohol molecules are hydrocarbons, hydrocarbons do not form hydrogen bonds with water molecules
What agents can be used to oxidise primary and secondary alcohols?
Acidified dichromate ions, H+/Cr2O7⁻⁷; Oxidising mixture could be, K2Cr2O7 + H2SO4
How you create propanal from propanol?
Gently heat acidified potassium dichromate, primary alcohol oxidised into aldehyde; C3H7OH + [O] =K2Cr2O7/H2SO4=> propanal + H2O
How do you create a carboxylic acid from propanol?
Strongly heat excess acidified potassium dichromate, Alcohol will completely oxidise, passing aldehyde stage, forming carboxylic acid; C3H7OH + 2[O] =K2Cr2O7/H2SO4=> Propanoic acid + H2O
What is the oxidation triangle?
Primary OH =[O]> Aldehyde =[O]> Carboxylic acid Secondary alcohol =[O]> Ketone =/> Tertiary alcohol =/> Reduction <=2[H]= Oxidation =[O]=>
What is reflux?
Continual boiling and condensing of a reaction mixture to ensure reaction takes place without content of flask boiling dry
Where is water in/out in a condenser?
Water in at bottom, further down; water out closer, on top
What is tollen’s reagaent?
[Ag(NH3)2]+ ion which are reduced to a silver mirror as it oxidises aldehydes to carboxylic acids
How do you test for aldehydes from ketones?
React with tollen’s reagent while heating, produce silver mirror
Which mechanism is dehydration of an alcohol?
Elimination; Nucleophilic O gives a pair to H+, C breaks bond to H2O+, Adjacent H attacks bond between C-C, Alkene produced and H2O
How do you dehydrate an alcohol?
Alcohols must have H on adjacent C from the C , OH is binded to; hot, concentrated H2SO4 , 180c
What is fehling’s solution?
CuH2O4S; Green suspension and red precipitate in presence of aldehyde CHO functional group; Negative result, absence of red precipitate
