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Organic chemistry Flashcards

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1
Q

2 main groups hydrocarbons are divided into

A

Aromatic and aliphatic

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2
Q

Aromatic hydrocarbons

A

The cyclic organic compounds which are stabilized by forming a cyclic delocalized cloud of π electrons are called aromatic compounds

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3
Q

simplest of aromatic hydrocarbon compounds

A

Benzene C6H6

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4
Q

Aliphatic hydrocarbons

A

Hydrocarbons consisting of only open carbon chains are called as acyclic aliphatic hydrocarbons while those with cyclic carbon chains are called alicyclic hydrocarbons. The aliphatic hydrocarbons are classified as alkanes, alkenes, and alkynes

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5
Q

Alcohols

A

Alcohols are compounds containing a hydroxyl group (–OH) attached to an alkyl group
An alkyl group is formally derived from an alkane by the removal of a hydrogen atom

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6
Q

Esters

A

Esters are compounds containing the COOR group

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7
Q

Amides

A

Amides are compounds containing the CONH2 group.

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8
Q

Ethers

A

Ethers are compounds containing an oxygen atom attached to two alkyl groups

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9
Q

Aldehydes

A

Aldehydes are compounds containing a carbonyl (C=O) group attached to an H atom

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10
Q

Ketones

A

Ketones are compounds containing a carbonyl (C=O) group attached to two carbon atoms each of which may belong to an alkyl or aryl group

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11
Q

aryl group

A

aryl is any functional group or substituent derived from an aromatic ring

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12
Q

Alkyl halides

A

Alkyl halides are compounds containing a halogen atom bonded to an alkyl group

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13
Q

Carboxylic acids

A

Carboxylic acids are compounds containing the carboxylic acid (COOH) group

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14
Q

Amines

A

Amines are compounds derived formally from ammonia by replacing its H atoms either by alkyl groups or aryl groups.

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15
Q

Lewis acids and bases

A

Lewis acids are compounds accepting a lone pair of electrons while Lewis bases donate a pair of electrons.

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16
Q

Nucleophiles and Electrophiles

A

chemical species that forms bonds with electrophiles by donating an electron pair. Because nucleophiles donate electrons, they are Lewis bases.

an atom or a molecule that in chemical reaction seeks an atom or molecule containing an electron pair available for bonding. Electrophilic substances are Lewis acids

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17
Q

Optically inactive and active compounds

A

Optically active compounds are compounds with chiral carbons while in optically inactive compounds chiral carbons are not found.

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18
Q

Priority order of functional groups

A

COOH, COOR, COCl, CONH2, CN, CHO, CO, OH, NH2, F, Cl, Br, I, NO2

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19
Q

Divisions and subdivisions of isomers of organic compounds

A

Constitutional isomers - chain, position and functional group
Stereoisomers - Enantiomers, Diasteromers

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20
Q

Stereoisomerism

A

Is the existence of compounds whose structures differ from each other only in the orientation of bonds in three-dimensional space.

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21
Q

Enantiomers

A

Pair of stereoisomers whose 3-dimensional structures are mirror images of each other.

compounds showing enantiomerism should contain a chiral carbon. When plane polarised light is passed through a solution containing only 1 enantiomer, the plane of polarisation rotates.

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22
Q

Diasteromers

A

Pair of stereoisomers whose 3-dimensional structures are not mirror images of each other.

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23
Q

Benzene ring with COOH

A

Benzenecarboxylic acid
Benzoic acid

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24
Q

Benzene ring with CH3

A

Toluene

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25
Q

Benzene ring with OH

A

Phenol

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26
Q

Benzene ring with NH2

A

Aniline

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27
Q

Benzene ring with COH

A

Benzenecarbaldehyde
Benzaldehyde

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28
Q

2 ways in which bond cleavage could occur

A

Heterolytic cleavage
Homolytic cleavage

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29
Q

Heterolytic and Homolytic cleavage

A

In heterolytic cleavage the 2 electrons involved in the bond will remain with 1of the atoms.
This will result in an anion and a cation.

In homolytic cleavage the 2 electrons involved in the bond will be equally divided to each atom.
This will result in 2 neutral free radicals

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30
Q

Free radicals

A

Uncharged molecules having an unpaired valency electron. They are highly reactive.

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31
Q

Neutral nucleophiles

A

NH3, H2O and SO2

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32
Q

Homologous series

A

If 2 consecutive members of a series of compounds differ only by a CH2 unit, such a series of compounds is called a homologous series.

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33
Q

Chain reactions

A

Sequence of reactions where the product of 1 reaction becomes the starting material for the subsequent reaction of the sequence.
Consist of chain initiation, propagation and termination.

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34
Q

Carbocations

A

Electron deficient positively charged trivalent carbon species
Classified as primary, secondary, tertiary and methyl

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35
Q

Solubility of carbocations

A

Tertiary > secondary > primary > methyl

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36
Q

Markovnikov’s rule

A

States that when a protic acid (HX) is added to an asymmetric alkene, the H atom is added to the carbon atom bonded to the highest number of H atoms.

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37
Q

Anti-Markovnikov’s rule

A

Hydrogen bonds are added in the opposite way when there are peroxides in the reaction medium.

In the presence of peroxides the reaction between HX and alkenes takes place via a free radical mechanism and not the ionic reaction

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38
Q

Halogen which does not react with alkynes

A

I2

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39
Q

Addition of H2O in the presence of Hg2+

A

Results in an enol (OH group) which is unstable and will rapidly convert to more stable aldehydes or ketones

Only ethynes will convert to aldehydes others will convert to ketones.

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40
Q

Acidic nature of alkynes with terminal hydrogen

A

Since a sp orbital has more s character (50% s character) than sp2 or sp3 orbitals, the bonding electrons in the C–H bond of alkynes are closer to the carbon nucleus than in the case of C–H bonds in alkenes and alkanes. Therefore the H attached to a triple bond carbon has a higher acidity than the H in alkene or alkane C–H bonds. However, the acidity of H attached to terminal alkynes is less than that of water and alcohol.

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41
Q

Who proposed a 6 membered ring of C atoms with alternating double and triple bond structure for benzene

A

Kakulé

However the structure of benzene is now considered to be a resonance hybrid of 2 kekulé structures.

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42
Q

resonance stabilization (or aromatic stabilization) energy of benzene

A

152 kJ mol-1

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43
Q

Characteristic reactions of benzene

A

Characteristic reactions of benzene are electrophilic substitution reactions and not electrophilic addition reactions as in the case of alkenes.

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44
Q

Arenium ion

A

Formation of a bond between the electrophile (E+) and a carbon atom in the benzene ring gives rise to a carbocation (arenium ion)

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45
Q

Acylium ion

A

R-C+=O

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46
Q

Resistance of benzene ring towards oxidation

A

Benzene does not get oxidized by normal oxidizing agents like KMnO4, K2Cr2O7. However, the alkyl substituted benzene can be oxidized into benzoic acid (white ppt)

Tertiary alkyl groups do not get oxidized under these conditions

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47
Q

Directing groups of mono substituted benzene

A

Ortho,para directing and activating group
Ortho,para directing and deactivating group
Meta directing and deactivating group

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48
Q

Ortho para directing groups

A

OH, R, NH2, NHR, OR

They activate the benzene ring towards electrophilic substitution by making it more electron rich than benzene

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49
Q

Ortho para directing and deactivating group

A

Cl, Br, I

50
Q

Meta directing and deactivating group

A

NO2, CHO, COR, COOH, COOR

They deactivate the benzene ring towards electrophilic substitution by withdrawing electrons from it

51
Q

Characteristics of alkyl halides

A

Polar compounds
Solubility in water is very low (they do not form H bonds with water)
Due the higher electronegativity of the halogen compared to the C atoms, C atom gets a slight positive charge, hence nucleophiles attack this position

Characteristic reactions of alkyl halides are nucleophilic substitution reactions

52
Q

Characteristic reactions of alkyl halides are

A

Nucleophilic substitution reactions

53
Q

Aryl halides

A

is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide.

54
Q

Vinyl halides

A

In organic chemistry, a vinyl halide is a compound with the formula CH₂=CHX.

55
Q

Restriction shown by aryl halides towards nucleophilic substitution reactions

A

Due to the resonance stabilization of the aryl halides.
Due to the resonance C-Cl bond becomes shorter and stronger compared to alkyl halides

56
Q

Restriction shown by vinyl halides towards nucleophilic substitution reactions

A

Due to the presence of resonance which introduce partial double bond character in C-halogen bond.

57
Q

Grignard reactions

A

Alkyl halides react with Mg in the medium of dry ether to form grignard reagent R-MgX

An electron deficient C atom is converted to electron rich C atom

Grignard reagents cannot be prepared or used in the presence of compounds which have weakly acidic H atoms including H2O

58
Q

Main 2 types of alcohols

A

Aliphatic
Aromatic

59
Q

According the no. of OH groups present alcohols are classified as

A

Monohydric
Dihydric
Trihydric
Polyhydric

60
Q

Boiling point of alcohols

A

Branching of the alkyl part of the molecule leads to a reduction of boiling point

Alcohols have boiling points greater than alkanes, ethers and alkyl chlorides.

61
Q

Water solubility of alcohols

A

Alcohols with low relative molecular masses are soluble in water

Accordingly the solubility of alcohols in water gradually decreases with increase in strength of London forces

62
Q

Compounds which readily dissolve in ethanol

A

NaOH, Hexane

63
Q

Alkoxide ion

A

RO-

64
Q

Main 2 types of reactions of alcohols

A

Reactions involving cleavage of OH bond
Reaction with alkali metals and esterification

Nucleophilic substitution reactions involving cleavage of CO bond

65
Q

Variation of acidic strength of terminal H of compounds

A

H20 > ROH > Alkynes > H2 > NH3 > RNH2

66
Q

Variation of basic strength of compounds

A

R- > NH2- > H- > H2 > RO- > HO-

67
Q

Alcohols react with carboxylic acids forming

A

Esters
conc.H2SO4 acts as a catalyst

68
Q

Inability in reaction by breaking OH bond as primary, secondary and tertiary

A

Polarisation of the OH bond decreases from primary to tertiary as the electron density of the C atom connected to the OH group increases from primary to tertiary

69
Q

Ability in reaction by breaking CO bond as primary, secondary and tertiary

A

Stability of the carbocations resulted due to the breaking of CO bond increases from primary to tertiary
Compounds tend to form stable compounds so that ability of braking the CO bond increases from primary to tertiary.

70
Q

Which reaction is used to distinguish between primary, secondary and tertiary alcohols

A

Lucas test, Lucas reagent contains anhydrous ZnCl2 and conc. HCl

71
Q

Lucas test

A

ZnCl2 acts as the catalyst which is an Lewis acid
ZnCl2 reacts with ROH forming alkyl halides RCl. As alkyl halides are insoluble in water (no H bonds), the solution becomes cloudy and turbid. Tertiary alcohols forms the turbidity in the shortest time as the intermediate carbocation formed is stable.

72
Q

Oxidation of primary, secondary and tertiary alcohols

A

Undergoes oxidation with acidified K2Cr2O7, KMnO4, CrO3 and PCC (Pyridinum Chlorochromate)

Primary alcohols from carboxylic acids, However when PCC (mild oxidising agent) is used reaction is stopped at the aldehyde stage.

Secondary alcohols forms ketones (with PCC also)

Tertiary alcohols does not undergo oxidation (no H atoms)

73
Q

Characteristics of phenols

A

Colourless crystalline solid compound
Red liquid in wet conditions
Dissolves in organic solvents
Solubility in water is very low

74
Q

Non occurrence of nucleophilic substitution reactions by breaking CO bond

A

Due to the resonance stability of benzene ring the CO bond is shorter and stronger.
The phenyl cation formed due to the breaking of CO bond is unstable

75
Q

Characteristic reaction of phenol

A

Electrophillic substitution reactions

76
Q

Bromination of phenol

A

Results in white ppt of 2,4,6-tribromophenol
Br should be on oath, para positions

77
Q

Acidic property of any compound depends on

A

Ability of releasing H+ ion
Stability of ion formed after releasing H+ ion

78
Q

Stability of phenoxide ion vs phenyl cation

A

Stability of phenoxide ion is greater compared to the stability of phenyl cation because on phenoxide ion is there is no + charge on O atom

79
Q

Acidity of phenol vs nitrophenol

A

NO2+ is a electron withdrawing group, Due to this OH bond in nitrophenol is more polarised than in phenol. This allows the breaking of OH bond easily releasing H+

80
Q

Variation of boiling points of O containing compounds

A

Carboxylic acid > alcohol > ketone > aldehyde > Ether > alkane

Branching part of the alkyl group leads to reduction in boiling points

81
Q

Water solubility of aldehydes and ketones

A

Aldehydes and ketones with relatively lower molecular masses are soluble in water

82
Q

Characteristic reaction of aldehydes and ketones

A

Nucleophillic addition

83
Q

Addition of HCN to aldehydes and ketones

A

Results in cyanohydrin

84
Q

Reaction with Grignard reagent (aldehydes and ketones)

A

Results in the formation of alkoxy magnesium halide which turns to the corresponding alcohol upon hydrolysis

Ketones form tertiary alcohol
Aldehydes form secondary alcohol
Formaldehyde (HCOH) form primary alcohol

85
Q

Reaction with 2,4-dinitrophenylhydrazine (2,4-DNP/ Brady reagent)

A

Forms 2,4-dinitrophenylhydrazone (Orange or yellow ppt)

86
Q

Acidic nature of aldehydes and ketones on self condensation

A

H atoms attached to the carbon atoms (Alpha carbon) directly bound to the carbonyl carbon (alpha hydrogen) becomes acidic. Carbanion so formed is stabilised by resonance.

87
Q

Aldehydes and ketones with alpha hydrogen undergo

A

Base catalysed self-condensation reactions

88
Q

Reduction of aldehydes and ketones is done using

A

LiAlH4 (Lithium aluminium hydride) or NaBH4 (Sodium promo hydride) or Zn/Hg/conc.HCl (Clemmenson reduction)

89
Q

Why LiAlH4 is used in ether medium

A

LiAlH4 is too reactive to be used in the presence of water or methanol

90
Q

Products formed due to the reduction of aldehydes and ketones by LiAlH4 / NaBH4

A

Ketones give secondary alcohols
Aldehydes give primary alcohols
Methanal gives methanol

91
Q

Oxidation aldehydes by Tollens reagent forms

A

Ag ppt (Silver mirror)

92
Q

Oxidation aldehydes by Fehlings reagent forms

A

Blue Cu (Tartrate) turns to Cu2O (Brick red ppt)

93
Q

Oxidation aldehydes by acidified KMnO4 forms

A

Mn2+ (pale pink)

94
Q

Oxidation aldehydes by acidified K2Cr2O7 forms

A

Cr3+ (green)

95
Q

Water solubility of carboxylic acids

A

Carboxylic acids with C1-C4 dissolve well in water
When the no. of carbon atom increases solubility decreases
Aromatic carboxylic acids are water insoluble
Almost all carboxylic acids soluble in organic solvents

96
Q

Reduction of carboxylic acids

A

Undergoes reduction with LiAlH4 to form alcohols

Carboxylic acids and its derivatives do not get reduced with NaBH4 which is a less powerful reducing agent

97
Q

Characteristic reactions of acid chlorides

A

Nucleophilic addition reaction

98
Q

Reaction of acid chlorides with alcohols and phenols

A

Forms esters

99
Q

Reaction of acid chlorides with ammonia and primary amines

A

With ammonia forms primary amides
With primary amines forms secondary amides

100
Q

Reaction of esters with dil.mineral salts

A

Esters react with dilute acids and give corresponding carboxylic acid and the alcohol

101
Q

Reaction of esters with NaOH(aq)

A

Esters when reacted with aqueous NaOH form the sodium salt of corresponding carboxylic acid and the alcohol.

102
Q

Reaction of esters with Grignard reagent

A

Esters react with Grignard reagents to give tertiary alcohols. In this reaction, the ester is first converted to a ketone which reacts rapidly with the Grignard reagent again to give the tertiary alcohol as the product.

It is not possible to stop the reaction at the ketone stage

103
Q

Reaction of esters with LiAlH4

A

Esters react with LiAlH4 and reduce to give alcohols.

Gives a mixture of alcohols

104
Q

Reaction of amides with NaOH(aq)

A

When amides are warmed with an aqueous solution of NaOH, the sodium salt of the corresponding carboxylic acid is formed with liberation of gaseous NH3

105
Q

Reduction of amides

A

Amides are reduced to the corresponding primary amine with LiAlH4

106
Q

Variation of boiling points of amines

A

Amines have lower boiling points than alcohols

Secondary amines have less B.P than primary amines because the no.of hydrogen bonds formed in secondary amine is less

107
Q

Basicity of aliphatic amines

A

Is more than ammonia

From primary to tertiary amines basicity increases

108
Q

Reaction of amines with alkyl halides

A

Forms tertiary amines. Thus formed tertiary amine can react with alkyl halide further, to give a quaternary ammonium salt.

109
Q

Reaction of primary amines with acid chlorides

A

Primary amines react with acid chlorides to give secondary amides.

110
Q

Reaction of amines with nitrous acid (NaNO2/HCl)

A

Primary amines react with nitrous acid to form diazonium salts. As alkyl diazonium salts are unstable they rapidly convert to alcohols with the evolution of nitrogen gas.

111
Q

Basicity of alcohols vs amines

A

amines are more basic than alcohols

112
Q

Basicity aliphatic amines vs aniline

A

Aliphatic primary amines are more basic than aniline.

Due to the resonance stabilisation of the aromatic ring of aniline, lone pair is not readily available for a proton.

113
Q

Basicity of amines vs amides

A

Amides are less basic than amines

It is because the pair of electrons on the nitrogen of the amide group is delocalized on to the carbonyl group by resonance

114
Q

Colour of diazonium chloride

A

Yellow liquid

115
Q

Reaction of diazonium salt with water

A

When aqueous solutions of diazonium salts are heated, phenols are formed.

116
Q

Reaction of diazonium salt with hypophosphorus acid (H3PO2)

A

When diazonium salts are treated with hypophosphorous acid (H3PO2), the diazonium group is replaced by an H atom.

117
Q

Reaction of diazonium salt with CuCl and CuBr

A

When diazonium salts are reacted with CuCl or CuBr, the corresponding aromatic halide is formed.

118
Q

Reaction of diazonium salt with phenol

A

Benzene diazonium chloride reacts with phenol in the presence of aqueous NaOH to give an orange coloured compound, and with β-naphthol (2-naphthol) in the presence of aqueous NaOH to give a red coloured compound.

119
Q

How to form an imine

A

RNH2 + ketone/aldehyde

120
Q

In the nomenclature order which comes first, aldehydes or ketones

A

Aldehydes

121
Q

Phenol does not react with

A

NaHCO3, Na2CO3

122
Q

Cracking is achieved by

A

Sending the heavier hydrocarbons through a heated catalyst usually of zeolite (compound of aluminium, silicon and oxygen)

Chemistry (15 decks)

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