3.3.5 - Alcohols Flashcards
How do you get a carboxylic acid from a primary alcohol? x4
Oxidation with
- XS acidified potassium dichromate
- Under reflux (20 mins)
- With concentrated H2SO4
How do you get an aldehyde from a primary alcohol? x4
Oxidation with
- Dilute acidified potassium dichromate
- Gentle heat
- Little H2SO4
When forming an aldehyde from a primary alcohol, how do you reduce evaporation of the product?
Receiver vessel in ice
When forming an aldehyde from a primary alcohol, which substance is left in the reaction vessel and which evaporates off?
Evaporates - ethanal (receiver vessel in ice to condense)
In flask - ethanol
What happens to the ions in potassium dichromate when an alcohol is oxidised?
Orange dichromate ions (V)
-> GREEN chromium ions (III)
Give the molecular formula of ethanol
C2H5OH
Uses of ethanol? x5
- Solvent in cosmetics
- Drug manufacturing
- Detergents
- Inks
- Alcoholic drinks
Two ways of producing ethanol?
Hydration of ethene and fermentation of glucose
What type of reaction occurs with the fermentation of glucose to ethanol?
Anaerobic respiration
How do you convert ethene to ethanol?
Pressure + phosphoric
Acid (catalyst)
Steam
Heat (high temp)
What temperature does the fermentation reaction of glucose occur at?
35 degrees C (as to not denature yeast enzymes)
State the equation for the fermentation reaction of glucose
C6H12O6 (aq) —yeast—> 2C2H5OH (aq)+ 2CO2 (g)
Crude oil versus glucose: compare renewability
Crude oil: non-renewable
Glucose: renewable
Crude oil versus glucose: compare rate of reaction
Crude oil: fast
Glucose: slow
Crude oil versus glucose: compare type of process
Crude oil: continuous
Glucose: batch
Crude oil versus glucose: compare purity of product
Crude oil: pure
Glucose: requires distillation (15% conc. ethanol)
How do you convert ethanol into ethene? x4 (Name and 3x conditions)
Elimination reaction
- Concentrated H2SO4
- Hot
- In XS
Nomenclature for compounds with the -OH group?
- OH is highest priority group: suffix -ol
- OH is lower priority group: prefix hydroxy-
Functional group of alcohols?
-OH
General formula of alcohols?
C2H2n+1OH
Difference between primary/secondary/tertiary alcohols?
Primary - carbon next to -OH has one R-group
Secondary - carbon next to -OH has two R-groups
Tertiary - carbon next to -OH has three R-groups
Bond angle in C-OH bond?
105 degrees (repulsion from 2x lone pairs of electrons on the oxygen)
Bond name in C-OH bond?
Trigonal pyramidal
Do alcohols have higher/lower/the same boiling points as alkanes of the same mass? Why?
Higher - hydrogen bonding can occur due to oxygen and hydrogen in -OH functional group; hydrogen bonding is strongest intermolecular force, whereas only IMF in alkanes is van der Waal forces (weaker); more energy required to overcome H-bond between alcohol molecules; higher bpt
Why are shorter chain alcohols more soluble in water?
The -OH group is dominant, so H-bonds form between the alcohol and water molecules. With longer hydrocarbon chains, the hydrocarbon chain is dominant over the -OH, so H-bonds do not form
Where does glucose come from in the production of ethanol?
Sugar beet/cane
Catalyst for the fermentation of glucose to ethanol?
Yeast! (yeast, baby)
A dehydrated alcohol forms _______ isomers
E/Z isomers (alkene product)
E/Z isomerism is a form of what?
Stereoisomerism
Primary alcohols oxidise to _____ then ______
Primary alcohols oxidise to ALDEHYDES then CARBOXYLIC ACIDS
Functional group of aldehydes?
-CO (carbonyl group) at end of carbon chain
Functional group of carboxylic acids?
-COOH
Secondary alcohols oxidise to _____
Ketones
Tertiary alcohols oxidise to _____
Nowt
Functional group of ketones?
-CO (carbonyl group) at middle of carbon chain
Describe the Tollen’s Reagent test
Ag+ + e- -> Ag(s) Silver mirror test AgNO3 in aqueous ammonia - gentle oxidising agent Warm Aldehydes - Yes Ketones - No
Describe the Fehling’s Solution test
Cu2+ +e- -> Cu+ Blue solution (aq) -> Brick red ppt (s) Gentle oxidising agent Warm Aldehydes - Yes Ketones - No
