alcohols Flashcards
alcohol homologous series
OH functional group and nothing else
general formula for alcohols
CnH2n+1 OH
when are alcohols formed
when halogenalkanes undergo nucleophilic substitution reactions with aqueous hydroxides
naming simple alcohols
-longest carbon chain- prefix
-suffix is OL
-include position number before OL in name
how to classify alcohols
by number of carbons bonded to one with hydroxyl group
primary alcohol
carbon with OH bonded to one other carbon
secondary alcohol
carbon with OH bonded to 2 other carbons
tertiary alcohol
carbon with OH bonded to three more carbons
diol
when alkane hydrogen replaced by 2 OH groups
naming diols
-write full name of longest chain
-suffix for diol end of chain name
-add position number for OH groups
-write position number of diol before each suffix and after prefix
Eg- hexane-2,2-diol
drawing alcohols
draw longest carbon chain
-position of OH group
-add OH extra when drawing diols
strongest IM force between alcohol molecules
hydrogen bonding
-compared to alkanes and alkenes they have strongest bonding
solubility of alcohols as chain increases
-polar molecules
-short ones highly soluble
-as it grows solubility decreases because greater region of chain non polar and non polar substances highly insoluble in polar solutes
carbonyl compounds
double bond C–O
aldehyde
when carbonyl bonded to carbon and hydrogen or two hydrogens
C double O and two H
general formula for aldehyde
CnH2nO
CHO structural formula
alkyl group
CH3Ch2CH2CH2
naming simple aldehydes
longest chain
-suffix is al
-always on end of carbon chain so dont add position name
ketone
when carbonyl of C–O bonded to 2 carbons
general formula for ketones
CnH2nO
structural formula of ketones
CH3COCH3
aldehyde structural formula
CH3CH2CHO
naming simple ketones
-longest carbon chain
suffix for ketone one
add position number because always on second carbon
eg pentanone
pentan-3-one
carbonyls
aldehyde
ketone
carboxylic acid
carboxylic acid
when C–O bonded to carbon and OH
general formula carboxylic acid
CnH2n+1 COOH
naming carboxylic acid
-prefix for longest chain
-suffix anoic acid
always at end of chain so no position name
drawing carbonyls
-carbon chain
aldehyde end of chain
-add ketone to position number carbon
-add COOH for anoic acid
IM forces of carbonyls
van der waal
dipole dipole
COOH have hydrogen bonding
oxidation in organic chem
whenever a carbon forms a bond with a more electronegative element
what do primary alcohols form when oxidised
aldehydes
what do secondary alcohols form when oxidised
ketones
why cant tertiary alcohols be oxidised
carbon hydrogen bonds break when oxidised but they dont have C-H bonds so dont oxidise
oxidising agent for alcohols
potassium dichromate
K2CR2O7
how to use potassium dichromate to oxidise alcohols
acidify
add dilute acid
-sulfuric acid normally
ethanol reaction with potassium dichromate
ethanol + Cr2O72- + H+ = ethanal + Cr(111) + water
chromium change of oxidation state
+6 from Cr2O72- to CR(111) 3+
reduced
colour change of oxidation of alcohols
orange to green
aldehyde oxidation product
carboxylic acid
half equations for oxidation of alcohols
1identify oxidising agent- Cr2O72 = Cr3+
-balance atoms- hydrogens with ions and water oxygens with water
-balance charges- add electrons in reactants side
symbol for oxidising agents
O with brackets around it
what happens during elminiation reactions
2 sigma bonds break and a pi bond forms
products of alcohol elimination reaction
alcohol = alkene + h20
elimination reaction catalyst
conc h2so4 or h3po4
external factors done in eliminaton reaction of alcohols
heat alcohol to increase rate of reaction
-use sulfuric acid or hydrogen phosphate
conditions for elimination reactions of alcohols
concentrated acid catalyst
-heat alcohol to speed up reaction
what to replace sulfuric catalyst with in mechanisms
H+ ions
how to remove alkene from preperation of dehydration reaction of alcohol
distilation
-strongest IM force pent1-ene has is van der waal but strongest alcohol has is hydrogen bonding so boiling point weaker so separate
where can hydrogens only be removed during alcohol reactions
hydrogens on carbons adjacent next to carbon with OH group
hydration of alkenes alcohol
alkenes + water reversible to alcohol
-double bond alkene plus water alkane plus OH group
steps of hydration alkene reaction
-add alkene in gas phase into reactor
-add water in form of steam
-add acid catalyst to start reaction
what type of reaction is hydration of alkenes
electrophilic addition
making alcohol from ethene
-convert to ethanol
phosphoric acid catalyst
-300 degrees
-compromise of yield and rate
-6000KPA
high pressure expensive but shift yield
-
equation for hydration of ethene
C2H4 +H2O REVERSIBLE C2H5OH
confitions of fermentation of yeast
no oxygen
-can contaminate ethanol to ethanoic acid
-oxygen can make co2 and h20
-temps 25 degrees no lower between 25 and 40
-temp any lower and slow rate and any higher and enzymes denature
advantages of fermentation
-renewable resources- plants
-more sustainable
-cheaper
-less energy used
disadvantages of hydration reactions
-non renewable reources
-more expensive
higher eneegy use
advantages of hydration
continuous process
-100 percent atom economy
-faster rate of reaction
disadvantages of fermentation
-slower rate of reaction
atom economy lower than 100 percent
-batch process not continuous
equation for reaction during fermentation
C6H12O6 = 2C2H5OH + 2CO2
carbon nuetral fuel
carbon taken in same as carbon let out during photosynthesis and combustion
-no overall co2 emissions
how to produce aldehydes
distill
how to produce ketones and carboxylic acids
heat under reflux
test for tertiary alcohols
add potassium dichromate and colour orange because cant be oxidised
test for secondary or primary alcohols
add potassium dichromate and solution will turn green
test for primary alcohol
tollens reagent
-silver mirror forms when aldehyde present
-no reaction for ketone
benedict or fehling for aldehydes
solution turns red when aldehyde present
-no change for ketone
-stay blue
