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Organic Chemistry Flashcards

1
Q

what is OC

A

study of carbon compounds other than its oxides, carbonates/hydrogencarbonates

organic means living/once lived

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2
Q

elements present in organic compounds

A

C and H always

O is common

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3
Q

what can C form and why

A

chains and rings of high molecular mass and complexity by joining together to an extent unlike any other element

C is invaraibly tetravalent in all its compounds - form 4 bonds

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4
Q

why are general organic reaction slow

A

compounds are covalent in nature

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5
Q

despite their properties ie low mp, insoluble, how can OCs undergo reaction

A

under special conditions

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6
Q

what are hydrocarbons

A

compounds of C and H only

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7
Q

what are source of hydrocarbons

A

fossil fuels since they burn exothermically and a major source of energy ‘

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8
Q

2 types of hydrocarbins

A

aliphatic- open carbon chain structure except cyclohydrocarbons
aromatic- closed chains, at least one benzene ring in structure

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9
Q

recall benzene structure

A

C6H8

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10
Q

what is empirical formula

A

smallest ratio of atoms in a molecule

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11
Q

whats molecular formula

A

actual no. and kind of atoms in a molecule

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12
Q

what is structural formula

A

actual no. kind and arrangement of atoms in a molecule

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13
Q

3 ways of writing structural formula

A
  1. displayed: shows all bonds
  2. condensed: putting all atoms around each C stom together and then separated with dots/dashs
  3. skeletal: all symbols for C and H removed as well as C-H bonds. all other bonds including C-C bonds shown
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14
Q

whats a functional group and what is the point of it

A

group of atoms/bond common to a class of compounds

determines characteristic chemical properties of compounds having that specific group

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15
Q

how are OCs classified into different homologous series

A

according to func. grp

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16
Q

steps to naming an organic compound using the IUPAC system ( for alkyl substituted alkanes)

A

1) -longest continuous carbon chain and name is according to no. of C atoms.
2) -number C atoms such that substituents position is on lowest possible C no.
- when numbering name of substituent must be before base name, and position of substituent must be before its name.
- func. grp appear on lowest C no.

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17
Q

how are halogenocompounds name

A

same as alkyl substituted alkanes

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18
Q

how are aliphatic alcohols and ketones named

A

same as alkenes ie modifying base name

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19
Q

what is the carbon no. of aliphatic aldehydes and carboxylic acid grps since they are always at the end of carbon chain

A

C1

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20
Q

how are amines named

A

using alkyl prefix followed by amine

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21
Q

if there are 2 grps then

A

they are put in alphabetic order

eg 2-bromo 2-methyl butane

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22
Q

general formula and functional group of alkenes

A

CnH2n

C=C

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23
Q

general formula and functional group of halogenoalkanes

A

CnH2n+1X

X

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24
Q

general formula and functional group of alcohols

A

CnH2n+1OH

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25
Q

general formula and functional group of aldehydes

A

CnH2n+1CHO

H-C=O

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26
Q

general formula and functional group of ketones

A

CnH2n+1COCmH2m+1

C bonded to to other Cs and =O

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27
Q

general formula and functional group of esters

A

CnH2n+1COOCmH2m+1

=OC-O-C

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28
Q

general formula and functional group of carboxylic acids

A

CnH2n+1COOH

O=C-OH

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29
Q

general formula and functional group of amines

A

CnH2n+1NH2

-NH2

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30
Q

general formula and functional group of nitriles

A

CnH2n+1CN

-C triple bond N

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31
Q

each stage in a reaction is called

and the overall reaction is the

A

an elementary reaction

overall equation, obtained by adding all element steps

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32
Q

series of steps in a reaction called

A

reaction mechanism

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33
Q

2 types of bond fission (breaking) in organic reaction

A
  • homolytic

- heterolytic

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34
Q

what is homolytic fission

A

covalent bond broken between2 atom so each atom retains its shared electron
results in formation of highly reactive species called free radicals- having unshared electron

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35
Q

heterolytic fission

A

covalent bond between 2 atoms broken so both electrons are gained by one of the two atoms
forms ions

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36
Q

what is a carbanion

A

group of atoms with a carbon atom carrying a negative charge, -ve ion formed from heterolytic fission

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37
Q

what is a carbocation

A

group of atoms with a carbon atom carrying a positive charge, +ve ion formed from heterolytic fission as carbon loses an electron

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38
Q

classification of carbon atoms in a chain

A 
primary, secondary, tertiary
1*- bonded to one other C
2*- 2 other Cs
3*- 3 other Cs
methylcation- single +ve C
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39
Q

classification of carboncations

A

based on nature of the carbon atom carrying the +ve charge

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40
Q

order of stability of carbocations

A

3>2>1*>methylcation

  • alkyl grps have an electron releasing effect called inductive effect (+I effect)
  • release electrons towards (not complete transfer, some cloud/charge) towards +ve C atom
  • results in distribution of +ve charge to other atoms, which increases its stability
  • as no. of alkyl grps around C+ increases so does stability due to more +ve charge spread
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41
Q

the more _ the carbocation, the more _ its formed

A

stable

readily

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42
Q

nucleophiles. what are they and their structure

A

electron rich species which attack electron deficient site in molecule

has at least 1 lone pair of electrons to donate to form a covalent bond with electron deficient atom

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43
Q

in general, nucleophiles are

eg

A

negatively charged ions or neutral molecules with an atom having atleast 1 lone pair
eg CN-, NH3

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44
Q

electrophiles are

A

electron deficient species which attack electron rich site of molecule
can be positiv

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45
Q

what they are and eg of electrophiles

A

can be +vely charged ions of neutral molecules which are short of electron to have an octet

eg H+, BF3

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46
Q

how many types of organic reactions

A

6

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47
Q

substitution

A

atom/grp of atoms replaced by another

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48
Q

addition

A

atoms/grp get added across multiple bond to form single product

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49
Q

elimination

A

atom/grps removed from adjacent carbon atoms to form a multiple bond
eg dehydration of alcohols water lost

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50
Q

hydrolysis

A

break down of bond/molecule by water

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51
Q

oxidation

A

addition on oxygen atoms to molecule and/or removal of hydrogen atoms from molecule

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52
Q

reduction

A

removal of oxygen and/or addition of hydrogen

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53
Q

alkanes form homologous series with general formula …
they are called saturated hydrocarbons because
sources:

A

CnH2n+2
carbon to carbon single bonds
crude oil/petroleum mainly, natural gas mainly methane

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54
Q

cycloalkanes are sat or unsat?

what is their structure?

A

saturated closed ring of carbon atoms

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55
Q

why dont cycloalkanes follow alkane general formula

A

2 end carbon atoms in an alkane chain bond to eachother to form closed ring. hence there are 2 less hydrogen atoms in it compared to corresponding alkane

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56
Q

why are alkanes generally unreactive

A

due to electronegativity difference between C and H is small. so they are non polar so cant be attacked by nucleo/electro philes

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57
Q

complete and incomplete combustion of alkanes

A

comp-they burn in excess oxygen to form CO2 and H2O

incomp- burn in insufficient oxygen to form CO and H2O

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58
Q

why is alkane incomp combustion of dangerous nature

A

CO is toxic gas it binds with haemoglobin and prevents O2 being carried around body by blood

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59
Q

hydrocarbon burning as fuels releases oxides of nitrogen into air leading to

A

acid rain

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60
Q

how are nitrogen oxides formed. give equations also for acid rain formation

A

N2 and O2 in air combine to form NO which gets oxidised to form NO2 in high temp and pressure of engine
N2+O2–>2NO colorless gas
NO+1/2O2–>NO2 brown
2NO2+H2O+1/2O2–>2HNO3

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61
Q

cars with catalytic converters in exhaust system what reactions follow after warming

A

-oxidation of CO to CO2
-reduction of nitrogen oxides to N2 gas
2NO+2CO–>N2+2CO2
-oxidation of unburnt hydrocarbons to form CO2 and H2O

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62
Q

what is a problem catalytic converter cant solve

A

cant control CO2 emission which is a greenhouse gas hence global warming

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63
Q

condition for alkanes to undergo substitution with halogens

A

UV light

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64
Q

what happens when alkanes undergo substitution with halogens

A

hydrogen atoms in alkane get replaced successively by a halogen atom to give a mixture of products

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65
Q

reaction mechanism for when alkanes undergo substitution with halogens

A

takes place via formation of free radicals so the mechanism called Free Radical Substitution

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66
Q

3 steps of Free Radical Substitution

A

1) initiation
2) propagation
3) termination

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67
Q

explain the initiation step when methane is substituted with chlorine

A

chorine molecule undergoes homolytic fission in presense of UV to form chlorine free radicals

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68
Q

explain the propagation step when methane is substituted with chlorine

A
  • chlorine radical being reactive (extra e) attacks alkane (nucleophilic attack) resulting in homolytic fission of a C-H bond to form a new radical and a HCl (halide) molecule (e given to C and H gained by Cl)
  • then the methyl radical attacks a Cl2 again forming substitution product and a chlorine free radical (e given to 1 Cl, other Cl gained by C)
  • since a chlorine free radical is released in 2nd step the 1st can happen again etc chain
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69
Q

explain the termination step when methane is substituted with chlorine

A

2 free radicals combine to form a single molecule as product.
reaction eventually comes to a stop as free radicals not formed
CH3+Cl—>CH4Cl
CH3+CH3–>CH3CH3 ethane

70
Q

practice naming organic compounds

71
Q

practice showing reaction mechanisms like for substitution

72
Q

general formula of alkenes

why are they termed unsaturated

73
Q

manufacture of alkenes

A

cracking of less petroleum fractions
larger alkane broken into mixture smaller alkanes and alkenes
carried out in absense of O2, at high temp, and catalyst ie Al2O3/SiO2
some H2 may form by breaking C-H bonds

74
Q

typical reaction of alkenes

75
Q

condition hydrogenation of alkenes

A

hydrogen and alkene passed over finely (particle size) divided (turnings) nickel (or platinum) catalyst at 140*C

76
Q

condition and importance of hydration of alkenes

A

steam and gaseous alkane reacted in presense of conc. phosphoric acid catalyst at a temp of 230*C and 60atm pressure

used in industry to make alcohols

77
Q

addition of hydrogen halides

A

alkene bubbled through conc. hydrogen halide solution at room temp it forms a halogenoalkane

78
Q

talk about the products formed when a hydrogen halide reacts with an unsymmetric alkene

A
  • mixture of 2 products eg 1 and 2 bromopropane
  • major product is 2 bromopropane
  • why? Markovnikov’s rule: hydrogen bonds to the carbon which already has more hydrogen atoms. aka halogen bonds to carbon with least H atoms in major product
  • 2 bromopropane is formed via formation of a secondary carbocation which more stable than a primary one and more stable the carbocation more readily it forms
79
Q

addition of halogens, X2 (aq) to alkenes

A

bubble/pass alkene through halogen alkene at room temp it forms a dihaloalkane

80
Q

test of unsaturation

A

reaction with bromine water is a test for alkenes. it gets decolorised when shaken with alkene (from orange-brown)

81
Q

what is reaction mechanism of addition called

A

electrophilic addition reaction

82
Q

generalise what happens in electrophilic addition reaction

A

1- addition of electrophile to form carbocation

2- carbocation undergoes a nucleophilic attack to form the addition product

83
Q

practice addition mechanisms

84
Q

mechanism for electrophilic addition of halogens to alkene

A
  • as Br2 and alkene approach each other high electron density around C=C repels the pair of electrons in the Br-Br bond away from the bromine atom which is closer to double bond.
  • this makes Br atom closer to the double bond slightly +ve and the atom further away slightly -ve
  • then br-br and c=c bonds break heterolytically. a new bond forms between Br+ and one of the carbon atoms to form a carbocation.
  • carbocation is attacked by nucleophile Br- to form addition product (C+ has lost so gets pair from Br:-)
85
Q

oxidation of alkenes condition

A

using powerful oxidising agents such as acidified potassium manganate (VII) aka potassium permanganate: KMnO4

86
Q

product of oxidation alkanes under cold, dil and hot, conc solution conditions

A
  • cold and dil KMnO4: alkenes undergo oxidation to form a diol. KMnO4 gets decolorised from purple
  • hot and conc KMnO4: c=c bond in alkene broken completely and a diol is formed in the 1st step which gets further oxidised to a ketone/aldehyde/carboxylic acid/CO2

remember reaction is with MnO4- ion, oxidising agent

87
Q

what does the product of alkene oxidation depend on

A

apart from conditions, the nature of what is bonded to the C atoms involved in c=c ie the alkyl groups

88
Q

oxidation of alkenes can be used to

A
  • locate position of double bond in an alkene

- this is done by identifying products of oxidation, then work back to deduce original alkene

89
Q

addition polymerisation (alkenes) importance

A

forms basis of plastic industry `

90
Q

polyalkenes are non bio degradable.
meaning,
why is this an issue (disposal),
what is the solution

A
  • do not decompose by help of microorganism so remain in soil for long
  • landfill sites, litter pollution, waste of agricultural land, on burning release harmful gases eg CO
  • recycling (but issue of sorting)
91
Q

typical reaction and mechanism of halogenoalkanes

A

substitution reaction

nucleophilic substitution reaction

92
Q

what happens in halogenoalkanes substitution with aq alkali (OH-)

A

aka hydrolysis to form alcohol, but with water itself the reaction is slow (because it ionises little so low OH- conc).
halogenoalkanes heated under reflux with aq NaOH, where OH- is the nucleophile and Na is spectatot

93
Q

rates of hydrolysis of halogenoalkanes and reason for trend

A

order of reactivity: fluroalkane is least, iodoalkane is most
increases down the group
because bond energy values of C-halo bond decrease down the grp

94
Q

halogenoalkane reaction with cyanide ion CN-

A

(alkane)nitrile formed as halogenoalkane heated under reflux with aq sodium/potassium cyanide in ethanol (ethanolic) which is solvent for OCs
nucleophile is cyanide ion

95
Q

why is halogenoalkane reaction with cyanide used as intermediate route in organic synthesis

A

increases no of carbon atoms in chain

96
Q

halogenoalkane substitution with ammonia

A

(alkyl)amine formed

ammonia is nucleophile (neutral with lone pair, not -ve ion)

97
Q

how are products of halogenoalkane substitution with ammonia classified

A

as 1,2,3* according to no of alkyl (R) grps around N. (no of H atoms to be replaced by R)

98
Q

what is done to get primary amine as major product in halogenoalkane+ammonia subst. and not mixture of 1, 2, 3*amines (why this happens if not too)

A

heat halogenoalkane under reflux with excess ammonia in ethanol under pressure

if ammonia not in excess mixture obtained because amine formed in each reaction acts as nucleophile and reacts with halogenoalkane

99
Q

mechanism of nucleophilic subst. in halogalkns

A

C atom bonded to halogen atom is polar due to E.n diff.
this C is electron deficient and is susceptible to nucleophilic attack.
2 possible mechanisms infact. they are determined by structure of halogenoalkane involved.
halogalkns can be classified as 1,2,3 ry which is based on nature of C bonded to halogen

100
Q

mechanism for primary halogenoalkanes in substitution (abbreviation, full form, general mechanism, steps)

A

SN2 mechanism
substitution nucleophilic bimolecular
-as OH- ions approach HA they donate pair of electrons to electron deficient C to form new covalent bond
at same time C-Halogen bond breaks by heterolytic fission
-1st step is formation of an intermidiate worthy attacking nucleophile; OH- and leaving halogen atom are partially bonded to C resulting in pentavalent carbon, which being crowded is unstable
-2nd step C-halo bond breaks to give subs product. faster than step 1

101
Q

mechanism for tertiary halogenoalkanes in substitution (abbreviation, full form, meaning of 1, steps)

A

SN1
substitution nucleophilic unimolecu;ar/first order. 1 tells us that in slowest step, which is rate determining step there is only 1 reactant species which is HA and rate of reaction depends of HA conc.
-1st step c-halo brond undergoes heterolytic fission to form carbocation
-2nd step carbocation attacked by nucleophile OH- to give subst product

102
Q

mechanism for 2ndry halogenoalkanes in substitution

A

either SN1 or SN2

103
Q

elemination reaction of halogenoalkanes what happens and condition

A

involves loss of hydrogen halide molecule aka halo and H atom removed from adjacent C to form alkene + hydrogen halide
sol of NaOH in ethanol ie ethanolic sodium hydroxide

104
Q

differ between halogenoalkane substitution and elimination reactions talking only about condition

A

sub- aq NaOH

eli- ethanolic NaOH

105
Q

ATTENTION! ANSWER CARD MISSING DUE TO MISSING NOTES

uses of halogenoalkanes

106
Q

func grp of alcohols

107
Q

what are alcohols with 1 hydroxyl grp called

A

monohydric alcohols

108
Q

how are alcohols classified as 1* etc

A

C no at which OH grp is bonded

109
Q

why do alcohols have relatively higher bp than other OCs of similar molecular mass

A

alcohols can join by hydrogen bonding

110
Q

combustion of alcohols in excess air forms

111
Q

ethanol is a _ bcos its made from _. also made by _

A

biofuel
plant matter ie sugar cane

glucose fermentation

112
Q

subst in alcohols to form haloalkanes what happens

A

OH replaced by halogen
nucleophilic substitution
C bonded to OH is partially +ve because C-O bond is polar making C open to nucleophilic attack

113
Q

reagents used to chlorinate alcohols

A

HCl (dry and made in site as and when needed in vessel) , phosphorus (V) chloride which is PCl5, PCl3, sulfur dichloride oxide which is SOCl2

114
Q

how are phosphorus (iii) bromide and iodide made to bromidate/iodate alcohols

A

heating bromine>iodine with red phosphorus

115
Q

learn reaction of NaCl and conc. H2SO4

116
Q

reaction of alcohol with Na metal

A

sodium (eth)oxide and H2 gas produced

can be used as test for alcohols

117
Q

ethoxide ion …

118
Q

esterification
how
condition

A

alcohols react reversibly with carboxylic acids to form an ester, ie condensation and water
~involves breaking of OH bond
heating acid and alcohol under refluc with conc HCl

119
Q

hydrolysis of an ester

how (2 ways)

A

heating under refluc with acid/alkali

  • acid hydrolysis: reverse of ester formation so ester broken down into alcohol and acid
  • alkali hydrolysis: not reversible, is complete reaction and forms sodium salt of acid and an alcohol
120
Q

use of esters

A

perfumes and food flavors cos they sweet smelling with fruity flavor

121
Q

dehydration of alcohols;
what it is
how its done

A

an elimination reaction in which water molecule is lost to form alkene

carried out by passing alcohol vapor over heated aluminium oxide catalyst.
also done using porous pot (ceramic pieces) or pumice as catalyst
conc. sulfuric/phosphoric acid can be used as catalyst. temp about 170*C

122
Q

oxidation of alcohols;

what does product depends on

reagent

A

class of alcohols and conditions used

acidified potassium dichromate (VI) sol K2Cr2O7

123
Q

mild oxidation of primary alcohols

how and what

A

alcohol warmed with acidified K2Cr2O7

primary alcohol oxidised to aldehyde + water

124
Q

strong oxidation of primary alcohols

how and what

A

relfux alcohol with oxidising agent

it first gets oxidised to aldehyde (+h2o) , then further oxidised to carboxylic acid

125
Q

oxidation of secondary alcohols

how and what

A

warmed wth acidified K2Cr2O7

oxidised to a ketone

126
Q

primary alcohols on mild and strong oxi form…

A

mild-aldehyde

strong-carboxylic acid

127
Q

secondary and tertiary alcohols on oxi

A

s-ketone (n=cant further get oxi)

t-does not undergo oxi

128
Q

what is observed during alcohol oxi

A

orange dichromate (VI) ions reduced to green chromium (III) ions (orange>red>green)

129
Q

how can oxi of alcohols be of use

A

identify classes of alcohols (as thier products differ)

130
Q

3 methods of carboxylic acid formation

A
  • strong oxidation of primary alcohols
  • oxidation of aldehydes
  • hydrolysis of nitriles: heating nitrile under reflux with dil. HCl (gives carboxylic acid+ammonium salt)
131
Q

typical reactions of carboxylic acids

A

are weak acids (dont fully ionise in water)

but undergo all those as acids, as they produce small amount of H+

132
Q

carboxylic acid + metal gives

A

salt and H2

133
Q

ethanoate ion

134
Q

carboxylic acid + alkali gives

A

salt and H2O

135
Q

carboxylic acid + carbonate/hydrogencarbonate gives

A

salt+H2O+CO2

136
Q

carboxylic acid + alcohol gives

A

ester + h2o

137
Q

reduction of carboxylic acids

  • gives
  • reagent
  • conditions
  • simplified symbol for reducing agent in equation
A
  • corresponding primary alcohol + water
  • lithium tetrahydudo aluminate (LiAlH4) / sodium tetrahydudo borate (NaBH4)
  • room temp, dry ether
  • [H]
138
Q

what is carbonyl func. grp

139
Q

to make an aldehyde
method stated
procedure
any reasons for something being done

A

oxidation of primary alcohols
oxidisng agent added dropwise to warm primary alcohol. aldehyde formed is then distilled off from vessel. this is possible as and when it forms because has lower bp than its corsp alcohol. this is done because aldehyde can get further oxidised.

140
Q

to make a ketone

procedure

A

oxidation of secondary alcohol to give ketone and water

heat alcohol with with oxidising agent

141
Q

reduction of aldehydes and ketones gives, reagent used

A

thier respective alcohols
al-1*
ke-2*

reducing agent used: NaBH4 (warm carbonyl with it) / LiAlH4 (room temp)
in dry ether
–lialh4 in dry either because reacts vigorously with water–

142
Q

aldehyde and ketone addition with hydrogen cyanide reaction mechanism called _ because _
product
condition

A

nucleophilic addition
bcos first step is addition of nucleophile followed by addition of electrophile

2-hydroxynitrile

HCN generated in site by reaction between sodium cyanide and dil H2SO4 (NaCN+H2SO4–>HCN+NaHSO4)

143
Q

aldehyde and ketone addition with hydrogen cyanide what exactly happens

A

C atom of C=O grp being electron deficient is attacked by nucleophile.

144
Q

use of aldehyde and ketone addition with hydrogen cyanide

A

synthetic chemistry ie designing molecules as it increases no of C atoms in chain
nitrile grp can be then easily hydrolysed to carboxylic acid or reduced to an amine

145
Q

hydrolysis of nitrile grp

how and products

A

heat under relfux with dil acid (adding H+, C///N breaks)

carboxylic acid +NH4+

146
Q

nitrile can be group reduced to _ using _

A

aminoalkane ie alkylamine

sodium and ethanol

147
Q

explain mechanism of nucleophilic addition in aldehydes and ketones

A

-carbonyl group C=O in al and ke is polar due to high EN of oxygen atoms. electrons in bond slightly shifted more towards O, making C slightly electron deficient. so C is p+ O is p-

  • in 1st step, C of C=O grp being e deficient is attacked by nucleophile CN-
  • 2nd step, -vely charged ion intermediate formed in 1st step reacts quickly with H+ from HCN to form addition product

-CN- ions act as catalyst so reaction can also be carried out by adding aq NaCN or KCN along with HCN to increase reaction rate

148
Q

test for aldehyde and ketone, result, how it works

A
  • test with 2,4 dinitrophenyl hydrazine (2,4 DNPH)
  • both al and ke give orange ppt when added to sol of 2,4 dnph in ethanol
  • al and ke undergo condensation (addition elimination) with 2,4 dnph to form ppt
149
Q

learn structure of 2,4 dnph

150
Q

3 tests to distinguish between aldehyde and ketone

A

1-test with tollens reagent
2-test with fehling sol
3-acidified potassium dichromate

151
Q

describe test with tollens reagent aka silver mirror test, result, and reason why it works

A
  • tollens reagent is aq sol of silver nitrate in excess ammonia called ammoniacal silver nitrate. has Ag+ iond do ehrn when warmed with aldehydes gets reduced to Ag atoms
  • Ag atoms form mirror on test tube side
  • ketone -ve result
  • happens bcos aldehydes are reducing agents and al gets oxidised to carb acid
152
Q

describe test with fehling sol and results

A
  • its alkaline sol with Cu(II)ions.
  • aldehyde being RA reduce Cu2+ to Cu+ forming brick red ppt of Cu(I)oxide. al oxidised to carboxylic acid
  • ketone -ve result
153
Q

describe test with acidified potassium dichromate to differ between aldehyde and ketone and the results

A
  • on heating with KMnO3 aldehyde oxi to carb acid and dichromate sol changes from orange to green
  • ketones no change as cant get oxi
154
Q

iododoam reaction makes _, is used to _

A

tri-iodomethane

identigy methyl-carbonyl compounds, that is aldehydes and ketones with a CH3-C=O grp in thier structure

155
Q

iododoam reaction procedure and steps :

A
  • warm compound with an alkaline sol of iodine eg NaOH+I2
  • 1)carbonyl compound halogenated ie 3H in CH3 get replaced by I
    2) product from 1st step hydrolysed to form yellow ppt of CHI3
156
Q

test for CH3CH(OH) grp in particular alcohols _

A
  • secondary alcohols which have RCH3CH(OH) grp
  • this grp gets oxidised by alkaline iodine solution to form a methyl-ketone, which then undergoes the 2 steps to form yellow ppt of triidodomethane and salt of acid
157
Q

2 types of isomerism in OCs

A

structural

stereo

158
Q

what is strucural isomerism

A

when more than one compound has the same molecular formula but different arrangement of atoms

159
Q

3 types of struc iso

A

position
func grp
chain

160
Q

explain position iso

A

isomers have same molecular formula but different positions of the func grp on same carbon chain

161
Q

explain func grp iso

A

isomers have same molecular formula but diff func grp

162
Q

explain chain iso

A
  • chain isomers have same molecular formula but differ in structure of carbon skeleton or chain length
  • so isomers due to branching
163
Q

what is stereo iso

A

isomers have same molecular formula and structural formula but diff arrangement of atoms or grps in 3D space

164
Q

2 types of stereo iso

A

cis-trans (geometric)
and
optical

165
Q

explain cis - trans iso / geometric

A
  • in molecules with unsaturated bonds eg C=C

- unlike C-C single bond, molecule cant be rotated about double bond because theres a pi bond that breaks when twisted

166
Q

explain optical iso

A
  • shown by molecules having an asymmetric carbon atom called chiral
  • chiral carbon atom C* is one that is bonded to 4 different atoms/grps
  • molecules with C* can exist as mirror images which are not superimposable. images called optical isomers/enantiomers
167
Q

why are mirror images of OCs called optical isomers

A

they have different ability to rotate the plane of polarised light (vibration in only 1 plane)

168
Q

what are dextrorotatory and leavorotatory isomers

A
  • d or + isomers rotate plane of polarised light in clockwise direction
  • l rotate plane in anticlockwise direction
169
Q

what happens if d and l isomers are present in equal amounts

A

optical activity cancelled

such a mixture is called racemic mixture

170
Q

3 types of OCs that show optical isomerism fo sho

A
  • 2 hydroxy carboxylic acids
  • 2 hydroxy alkanoic acids
  • 2 amino carboxylic acids

AS Chemistry (11 decks)

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