Organic: Alcohols Flashcards
what is the general formula of alcohols
CnH2n+ 1OH
explain the classification of different alcohols
primary- OH is bonded to the first carbon in the chain propan-1-ol
secondary–OH is bonded to the second carbon on the chain pronal-2-ol
teirtiary-OH is bonded to the third carbon on the chain 2 methyl propan-2-ol
describe the properties of alcohols in terms of bp compared to alkanes/enes
alcohols have higher melting/boiling points than alkanes/akenes even with the same molecular mass due to alcohols having hydrogen bonding
are alcohols soluble and what property is involved
hydrigen bonding makes the shorter chain alcohols soluble in water as hydrogen bonds can form between OH groups and water molecules
what are the two processes used to manufacture ethanol?
by fermentation of sugars
by using ethene
Explain points of making ethanol from fermentation of sugars
C6H12O6 –>. 2C2H5OH + 2 CO2. enzymes from yeast
renewable raw material used in a batch process by fermentation
but not pure as 15% water obtained
fractional distillation used to make pure ethanol
ehtanol is a biofuel because it is made from plants that are renewable
explain the reaction of ethene with steam to produce ethanol
CH2=CH2 + H2O —> C2H5OH
ethene from crude oil a non renewable resource
with the presence of phosphoric acid in an electrophilic addition reaction under gaseous ethene and steam with H3PO4 as catalyst conditions
fast reaction, continuous process, 100% yield so its pure
reminder must learn mechanism here
what is the process of making and burning bioethanol
photosynthesis- 6CO2 + 6H2O —> C6H12O6 + 6O2
fermentation- CH=6H12O6 —> 2 C2H5OH + 2CO2
combustion- 2c2h5oh + 6o2 –> 4CO2 + 6H2O
important note: this process is carbon nuetral- LEARN WHY
by oxidising primary alcohols what is formed
Primary alcohols can be oxidised to form aldehydes - under distillation conditions with H+/Cr2O72- (acidified)
which can undergo further oxidation to form carboxylic acids- under reflux conditions with excess h+//CR2O72-
propan-1-ol to propanal + H2O
pronalal to pronation acid + H20
what colour change occurs for acidified dichromate
Acidified means that the potassium dichromate(VI) an orange oxidising agent is in a solution of dilute acid (such as dilute sulfuric acid)
For potassium dichromate(VI) to act as an oxidising agent, it itself needs to be reduced
This reduction requires hydrogen (H+) ions which are provided by the acidic medium
When alcohols are oxidised the orange dichromate ions (Cr2O72-) are reduced to green Cr3+ ions
orange to green
by oxidising secondary alcohols what is formed
secondary alcohols can be oxidised with H+/Cr2O72- to produce ketones, ketones are resistant to oxidation so no further reactions occur, because no more C-H bonds on the ketone
butan-2ol- to butanone +h2o
by oxidising tertiary alcohols what is formed
Teirtiary alcohols are resistant to oxidation because there are no C-H bonds on the C with the OH group
write a simple diagram of primary, secondary and tertiary alcohols with [O]
primary + [O] = aldehyde —> + [O] = carboxylic acid
secondary + [O] = ketone —> +[O] = no reaction
tertiary +[O] = no reaction
explain how to distinguish if the sample is a tertiary alcohol
if the alcohol is not oxidised by acidified potassium dichromate and remains orange then it is tertiary
what test can be done to distinguish between ketones and aldehydes
Tollens reagent: ( [Ag(NH3)2] )
tellens reagent is made by adding ammonia to silver nitrate, giving silver ions in ammonia
it is a weak oxidising agent so will have no effect on a ketone but the aldehyde will be oxidised and Ag+ is reduced to silver when the aldehyde is warmed with the tollens reagent a silver mirror will form inside the test tube-
there is no reaction with a ketone
Fehlings solution:
when blue fehlings solution is warmed with an aldehyde the blue copper II complex changed to dark brick red copper I precipitate (Cu2O)
There is no reaction with a ketone
