Module 4 - Alcohols Flashcards
name the general formula of alcohols
Cn H2n+1 OH
describe the structure of alcohols
-the OH replaces a H in a basic hydrocarbon skeleton
-bonds between the atoms are covalent
name the different classifications of alcohols
-primary (bonded to 1 carbon)
-secondary (bonded to 2 carbons)
-tertiary (bonded to 3 carbons)
describe how to classify alcohols
-according to the environment of the OH group
-depending on how many carbons the C-OH is bonded to
describe the boiling points of alcohols
-higher boiling points than similar molecular mass alkanes
-due to intermolecular hydrogen bonding
-so more energy is required to separate the molecules
-straight chain isomers have higher boiling points
describe the solvent properties of alcohols
-low molecular mass alcohols are soluble in water
-due to hydrogen bonding between the two molecules
-heavier alcohols are less soluble
-smaller alcohols (3+ carbons) soluble as can form hydrogen bonds with water
-can dissolve a large number of organic molecules as the polarity of OH group attracts other molecules
describe the combustion of alcohols
-combust more readily than their hydrocarbon equivalents
-added to petrol to increase efficiency of combustion
describe the use of oxidation of alcohols
-to differentiate between primary, secondary and tertiary alcohols
name the reagent used for oxidation of alcohols
-acidified potassium dichromate (VI)
observation when oxidation of alcohols occurs
-potassium dichromate (VI) turns from orange to green
describe the oxidation of primary alcohols
-oxidised to aldehydes with distillation
-oxidised to carboxylic acids with reflux
describe the oxidation of secondary alcohols
-easily oxidised to ketones
-using distillation or reflux
describe the oxidation of tertiary alcohols
-not oxidised
equation for distillation of primary alcohols
eg.
CH3CH2OH (l) + [O] -> CH3CHO (l) + H2O (l)
describe the process of distillation of alcohols
- alcohol is dripped into a warm solution of acidified K2Cr2O7
- aldehydes have low boiling points as they have no hydrogen bonding, so they distill off immediately
- if it didn’t distill off it would be oxidised to the equivalent carboxylic acid
equation for reflux of alcohols eg. CH3CH2OH
eg.
CH3CH2OH (l) + 2[O] -> CH3COOH (l) + H2O
equation for oxidation of secondary alcohols eg.
CH3CHOHCH3
eg.
CH3CHOHCH3 (l) + [O] -> CH3COCH3 (l) + H2O (l)
reagent for dehydration of alcohols
-concentrated sulphuric acid
or
-concentrated phosphoric acid
conditions for dehydration of alcohols
-reflux at 180 degrees
product for dehydration of alcohols
alkene
equation for dehydration of alcohols eg. C2H5OH
eg.
C2H5OH (l) -> CH2=CH2 (g) + H2O (l)
define a dehydration reaction
-removal of a water molecule from a molecule
describe dehydration in unsymmetrical alcohols
-can give more than one product
-when the double bond forms between different carbon atoms
describe why tertiary alcohols cannot be oxidised
-there is no hydrogen atom bonded to the carbon with the OH group
reagent for substitution reaction/bromination of alcohols
-sodium bromide
and
-concentrated sulphuric acid
conditions for substitution reaction/bromination of alcohols
reflux
product for substitution reaction/bromination of alcohols
haloalkane
equation for substitution reaction/bromination of alcohols eg. C2H5OH
eg.
C2H5OH (l) + NaBr (aq) -> C2H5Br (l) + NaOH (l)
describe the volatility of alcohols
-low volatility
-as they have high boiling points
-so they are not easy to vapourise
