topic 6e: alcohols Flashcards
primary alcohol
OH group bonded to a C bonded to only 1 other carbon atom
combustino of alcohols produces
carbon dioxide and water (complete)
halogenation
-OH is replaced bya halogen
how to holgenate to add chlorine
PCL5
ALCOHOLS REACTION WITH pcl5 product
- POCl3 + HCl + chloroalkane
- STEAMY FUMES OF HCl
alcohols + PCl5 observation
steamy fumes (HCl gas)
chlorination of TERTIARY Alcohols
- shake with HCl at room temp
- forms compound + H2O
how to do iodination
- red phosphorus + iodine
- heat under reflux
- 2P + 3I2 = 2PI3
- alc + PI3 = halkane + h3po3
products of iodination
- haloalkane
- H3PO3
(phosphoric acid)
how to dehydrate alcohol (elimination)
- heat with a concentratred phosphoric acid
forms an alkene
dehydration (elimination) alcohol product
alkene + water
primary alcohols oxidise to …
ALDEHYDES (then to carboxylic acids)
seconadry alcohols oxidise to
KETONS
tertiary alcohols oxidise to
do not oxidise
usual oxidisiing agent
acidified potassium dichromate
K2Cr2O7 in DILUTE sulfuric acid
colour change oxidation of alcohols
orange (cr207)2- to green cr3+
cr2o7 2- colour
orange
cr 3+ colour
green
how to bromonate
- potassium bromide + 50% sulfuric acid to form HBr. REFLUXXXXXXXXX
- HBr + alc = halkane + h2o
reaction for potassium bromide + 50% conc sulfuric acid
2KBr+H2SO4 = K2SO4 + 2HBr
why does aldehyde need to be distilled off as soon as its formed
so it doesnt further oxidise to a carboxylic acid
heating under reflux
- FULL OXIDATION eg carboxylic acid from primary, keton from secondary
- products of oxidation remain in the reaction mixture; condense and then return to the heating flask
- OPEN TOP!!!!!!
DISTILLATION
- PARTIAL oxidation eg aldehyde from primary alcohol
- aldehyde is dsitilled off as its formed, (lower BP than alcohol)
- collected in the receiver
what to change to go from distillation to heat under reflux
- open top condsner
- vertical condenser
why is x more soluble in ETHANOL than in WATER (2)
- water has 2 h bonds/ molecule, ethanol only 1
- h bonding in water stornger, requires more enegy to break
why is yield low of the aldehyde when heating under reflux?
- aldehyde is condesned
- fully oxidises to a carboxylic acid
purpose of anti bumping granules
-provides a surface for bubbles to form
- PREVENTS LARGE BUBBLES FROM FORMING
why are SMALL alcohols soluble in water?
- h bonds in water and in alcohols
- of similar strenght
- therefore h bonds form between the 2
why are larger alcohols less soluble?
- proporition of molecule that can H Bond is smaller
- ## LF in alcohol stronger
ethanol from ethene (hydration of ethene)
- ethene + steam
- phosphoric (V) acid CATALYST
- 300 degrees
- 60-70 atmospheres
ethanol can also be made by…
fermentation
stereoisomers (2)
- same structural formula
- sifferent arrangement in space
3 reasons for lower yeild
- transfer losses (residue left on apparatus)
- incomplete
- side reactions
why not use distillation to produce carboxylic acid
- produces aldehyde
- aldehyde will distil as soon as produced (before it turns into carboxylic acid)
how to dry organic layer to preapre for distillation (2)
- mix with drying agent eg anhydrous cacl2
- leave until adding drying agent doesnt clump together
how to improve distillation
- add antibumbing granules
- surface for bubbles to form
-thermometer should be opposite entrance of condenser - collecting over wrong temperature range
- ## add more ice water
why add sodium hydrogen carbonate in the experiment?
- react with HCl
- to release CO2
drying agent
sodium sulfate
calcium chloride
thermometer in experiment distillation must be
OPPOSITE TO OPENING OF CONDENSER
in reactions, water enters the … of the condsner
BOTTOM
conical flask in distillation must be …
open
why no stopper in reflux?
so pressure doesnt build up
why might you se brown vapour in bromonation?
- Br2 gas produced
-bromide ions have been oxidised by the acid
why add HCl in the experiment?
remove any unreacted alcohol
why open tap from time to time?
prevent build up of pressure (allow co2 to escape)
explain why reaction is slow, then speeds up, then slows
- slow due to repulsion
- speeds up as mn2+ autocatalytic
- slows down cos conc reactants decreases
fermentation
glucoe = ethanol +co2
fermentation conditions
- anaerobic
- yeast
- 25-42 degrees c
why can fermentation thought to be NOT carbon neutral
co2 emissions with vehicles for transporting
how to turn a halogenoalkane into an alcohol
- sodium hydroxide
- aqueous
- heat under reflux
NUCLEOPHILIC SUBSTIUTION
HYDRATION OF ETHENE name of mechanism
electrophilic addition
WHY DONT TERTIARY OXIDISE
- no H atom on central carbon
why hydration of ethene over fermentation
- fast reaction
- purer product2
alkene to diol
add acidified potassium 2 manganate (H3PO3)
