Alcohols Flashcards
General formula of alcohols
CnH2n+1OH
Polygydric alcohols
Alcohols containing more than one OH group
bp off alcohols in relation to alkanes 2
Higher than alkanes with the same number of C atoms (and les ls volatile)
Difference in bp decreases as chain length increases
In relation to intermolecular forces, why do alkanes have lower bp than alcohols
Alkanes: Non polar molecules so weaker London forces between molecules
Alcohols: Polar molecules, form stronger H bonds between molecules
Difference in energy req to overcome forces
Solubility in water of alcohols vs alkanes, why
Alcohols are more soluble in water bc the -OH forms H bonds to water molecules
Why and how does solubility of alcohols change as chain length increases 3
Hydrocarbon chain is non polar
So cannot form H bonds with water molecules
So solubility of alcohols decreases as chain length increases (only small chain are soluble)
How does viscosity of alcohols change as number of OH groups increase, why
Viscosity increases bc more H bonds can form between molecules, req more energy to overcome
Primary alcohol
The OH carbon is directly bonded to only one other carbon/ had 2 H
Secondary alcohol
The OH carbon is bonded directly to 2 othe Cs/ has 1 H
Tertiary alcohol
The OH carbon is has 3 other carbons bonded/ no H
Why do alcohols undergo complete combustion with less O2 than alkanes
Bc they already have an O in their formula
What state are small chain alcohols, benefit?
Liquid, makes them easily transportable so good fuels
Reflux? when is it used
Method of continuous heating of volatile reactants without any loss
Used when taking reactions to completion
Reflux?
Distillation (distill)
Means of separating liquids based on their boiling points
Dehydration reaction?
Water molecule is removed from the starting material (elimination)
Process/ conditions of dehydration of alcohols
Heat under reflux in the presence of an acid catalyst
Acid catalysts that can be used in reflux?
Concentrated phosphoric or sulfuric acid
Reactants in the substitution of the OH in alcohols
NaBr, H2SO4, Alcohol
Products of ‘side reaction’ of NaBr and H2SO4 in overall substitution reaction of alcohols
HBr is formed in situ (goes on to react with the alcohol)
NaHSO4 (does not partake in substitution)
Condition req in substitution of alcohols
Reflux
Is benzene with -OH group an alcohol
No, it’s a phenol
What type of condenser does reflux use vs distillation
Vertical vs side mouthed
What are the products of dehydration of alcohols
Alkene and water
Final products if substitution of alcohols
Haloalkane, water, sodium sulfate
Oxidizing agent in the oxidation of alcohols
Acidified (by sulfuric acid) dichromate ions: H+/Cr2O7-
Explain and give the colour change of dichromate ions
As an oxidizing agent, the orange Dichromate (VI) ions themselves are reduced to Chromium (III) ions which are green
Conditions and products of incomplete oxidation of 1° alcohols
Distill, [O],
Alderhyde, water
Conditions and products of complete oxidation of 2°
Reflux, [O]
Carboxylic acids, water
Conditions and products of complete oxidation of 2°
Reflux, [O]
ketone, water
Can 3° be oxidised, why
No, in oxidation another H from the C bound to the OH group should be donated, 3° do not have any H bound to the OH carbon
FG of alderhydes and suffix
-COH
-al
FG of ketones and suffix
-CO
-one
What is the name of the group ketones and alderhydes have in common
carbonyl
Ketones is found in middle of chain
Alderhydes must be at end of chain
How are molecules containing a hydroxyl group and other groups of higher priority named
Prefix hydroxy- is used
Oxidation vs Reduction regarding organic compounds
Oxidation is loss of H, gain of O
Reduction is gain of H, loss of O
