Fundamentals of Organic Chemistry: Isomerism and Nomenclature
1.ISOMERISM:-
The organic compounds having the same molecular formula but having different structural formula or we can say having different physical and chemical properties are called Isomers and the phenomenon is known as Isomerism.
Classification of Isomerism:-
Isomerism are classified into two categories:-1.Structural 2.Isomerism Stereoisomerism (ISOMERISM)
-(Structural Isomerism)-Chain Isomerism, Position Isomerism, Functional Isomerism, Ring- Chain Isomerism,Metamerism, Tautomerism.(Stereoisomerism)-Configurational, Isomerism, Geometrical,Optical,Conformational Isomerism Chain Isomerism
When the compounds having same molecular formula but they have different principle carbon chain then this type of isomerism is known as Chain Isomerism.CH3-CH2-CH2-CH3 (Butane), CH3-CH-CH3 1 CH3 (2-methyl-propane)
Position Isomerism
When the compounds having same molecular formula but they and same principle carbon chain but they have different positions of substitution y =l equiv bond or functional group, then this type of isomerism known as Position Isomerism. C*H_{2} = CH – C*H_{2} – C*H_{3} (But – 1 – ene) ,C*H_{3} – CH =CH-CH3 (8vt – 2 – ene)
Functional Isomerism
When the compounds having the same molecular formula but they contains different functional group, then this type of isomerism is known as Functional Isomerism (ethanol) C*H_{3} – C*H_{2} – OH,CH3 0 CH3 (dimethyl ether)
Ring Chain Isomerism when the compounds having the same molecular formula but they have different mode of linkage of carbon atoms (means one is in open chain and other is in closed chain) then this type of isomerism is known as Ring chain isomerism.CH3-CH2-CH=CH2 (Butene) (Cyclobutane)
Metamerism
When the compounds having the same molecular formula and same functional group but they have different arrangment of Carbon atoms on both side of functional group, then this type of isomerism is known as Metamerism. CH3-CH2-O-CH2-CH3 (Diethyl ether),CH3-CH2-CH2-CH3 (Methyl propyl ether).
Tautomerism when two compounds having the same molecular formula exist in two interconvertible different structures (dynamic equillibrium) then this type of isomerism is known as
2.IUPAC
The word IUPAC stands for International Union of Pure and Applied Chemistry.The purpose of IUPAC system of nomenclature is to establish an international standard of naming compounds to facilitate communication.(IUPAC)
-(Prefix)-Substituents, Cyclo/Bicyclo. (Word Root)-No. Of Carbon,in main chain.(Suffix)-Type of Bond, Functional group.
IUPAC
2º Prefix + 1° Prefix + Word Root + 1° Suffix + 2° Suffix Note:
Here 1° Primary e 2º = Secondary SUBSTITUENTS :-
CH3 : Methyl, C2H5 : Ethyl,C3H7 : Propyl,Br : Bromo,CI : Chloro,F : Fluoro,NO2 : Nitro,I:Todo.
TYPES OF BOND (一)Bond: ane (=) Bond: ene (=) Bond: yne.
WORD ROOT
1Carbon: Meth 2Carbon : Eth 3Carbon : Prop 4 Carbon : But 5Carbon : Pent 6Carbon : Hex 7Carbon : Hept 8Carbon : Oct 9Carbon : Non 10Carbon : Dec FUNCTIONAL GROUPS–
OH :Alcohol (ol),-CHO: Aldehyde (al),-R-C-R: ketone (one),-COOH: Carboxylic acid (oic acid),R-C-OR, = Alkyl Atk Ester (Alkyl Alkancak),R-O-R’ Ether (Alkoxy Alkane)
RULES FOR IUPAC NOMENCLATURE
Longest Chain Rule Select the longest C-C chain (May or may not be straight) CH3-CH2-CH2-CH-CH2-CH31 CH3 Wrong (x)CH3-CH2-CH2-CH-CH2-CH3 CH3 Right (v) Numbering from that side, so that branch (substituents) gets lowest locant.When more than 1 branch is present then follow lowest sum rule’ or First Point Of Difference.
Naming of Complex Substituents
While naming of complex substituents, Give 1st no to directly attached carbon from main chain, then follow IUPAC for substituents (Name written in Bracket)
Naming always done alphabetically
2-Bromo-4-ethye-6-methye Heptane
Naming of Cycloalkanes
While naming of carbocyclic compounds, we have to add the prefix Cyclo’ before the main chain.If ring and chain both have same number of carbons then For main chain Ring > Chain CH2-CH2-CH2-CH3[1-butyl Cyclobutane] Naming of Unsaturated Hydrocarbons, (Alkene Alkyne)simultaneously, select one with maximum / bonds (irrespective of no of carbons).In cycloalkenes and cycloalkynes both 1st and 2nd position is obtained by / bonds.
Naming of Functional Group
Functional groups are the atoms, or group of atoms which gives all properties to a compound.
Biggest and Final Rule For IUPAC Naming
Select longest C-C Chain containing
3.E1 & E2 REACTION
E1 and Es readions are nothing but the part of Elimination Reaction.An Elimination reaction is a type of organic reaction in which two substituents are removed from a molecule either in one or two steps.The one step mechanism is known as Es Reaction while the two step mechanism is known as Et Reaction. Elimination reaction is nothing but a method of preparation of Alkenes.The Degree of Unsaturation increases with Elimination Reaction.
TYPES OF ELIMINATION REACTION
Elimination reaction are of two types: E1 Reaction-E2 Reaction E1 REACTION
E+ Reaction stands for Unimolecular Elimination Reaction. It is a two step process. This reaction follows First order kinetics. Weak base used in Et Reactions. The reaction is proceed at high temperature.
STEP – I
Formation of Carbocation (Rate Determining Step)
STEP-Ⅱ
Loss of proton from the carbon atom adjacent to the carbon containing positive charge.
E2 REACTION
E2 reaction stands for Bimolecular Elimination Reaction. It is a one step process. The reaction follows second order kinetics. Strong base used in Ea reaction. The reaction is proceed at high temperatuse. The reaction is endothermic.
E2 REACTION
MECHANISMCH2 CHa CH2CH2 + H2O + kBr H Br E1 REACTIONS
It is a unimolecular elimination. It follows 1st order kinetics. It is a two step process. It requires weak base. Formation of carbocation takes place E2 REACTION.
It is a bimdecular elimination. It follows 2nd order kinetics. It is a one step process. It requires strong base. No carbocation formation takes place.
Factors Affecting Et & Ea Reaction
Carbocation Formation:-
Formation of carbocation is a slow e rate determining step in Er reaction. Increasing the number of substituent CR-Group) on C- atom increases the stability of carbocation that ultimately increases rate of E Reaction.
Leaving Group:
More easily the leaving group (halogens) removecl from carbon faster will be the Elimination Reactions.
R-IR>Br> R-CI > R-
FMature of Base by
In E₁ reaction the base used should be weak because if strong base is used then the reaction. Will be converted into E2.
Solvent Used:
Generally polar protic solvents are used in elimination reactions as they reduces the force of attraction between carbone
4.MARKOVNIKOV’S and ANTI MARKOVNIKOV’S:-
The rule or principle was given by russian chemist Markovnikov. According to Markovnikov’s rule during the addition reactions of alkenes the hydrogen atom (H+) is added to that carbon atom which has maximum number of hydrogen atom. The rule is basically given of unsymmetrical Alkenes.Markovnikov’s rule can also be explained in an another way that during the addition reaction of unsymmetrical alkenes the negative part of the adding reagent is added to that carbon atom which has minimum number of hydrogen atom.Example:-CH3-CHCH2-HBr CH3-CH CHa 1 Br ! H Mechanism-
STEP – I Formation of Carbocation (twa carbocation formation possible)STEP-II Attack of Nucleophile to 2º carbocation.
ANTI MARKOVNIKOV’S RULE
The rule was given by american scientist MS. Kharasch. This rule is also known as ‘kharasch Effect’ or ‘Peroxide Effect’. According to Anti-Markovnikov’s rule if the addition readions, of unsymmetrical alkenes are performed in the presence of Organic Peroxides (R-0-0-R) then Hydrogen atom is added to the carbon atom having minimum number of Hydrogen.
Mechanism
STEP-I Peroxides dissociates to give alkoxy free radicals.STEP-II Alkoxy free radicals attacks on HBr to form bromine free radical STEP-III Bromine free radical altacks on alkene to give 1º e 2º free radicals. STEP-IV More stable free radical (20) reacts with HBr to give final produce 5.OZONOLYSIS is a type of chemical reaction in which ozone is passed through an Alkene in an inert solvent like CCl4 to form Ozonide. Ozonides are explosive compounds hence they are are further reacted in the presence of zinc and water to give carbonyl compounds CAldehyde and ketones). Ozoholysis is basically a method of cleavage (breakage) of Alkene double bonds by reaction with ozane. (Os)
6.SAYTZEFF’S RULE
Saytzeff’s rule is also known as Zaitsev’s Rule. In the Elimination reactions when the Alkyl halide group have two or more ẞ carbon then more than 1 alkene product is formed. Now Saytzefl’s rule states that if more than 1 Alkene produck is formed as a result of elimination reaction then The Highly Substituted Alkene will be the Major Product of the reaction.
7.SP3 HYBRIDIZATION IN ALKANES
All the carbons of alkanes, shows sp³ Hybridization. In sp³ hybridization one s orbital combines with three porbitals to form four equivalent sp³ hybrid orbitals Each sp³ hybrid orbital shows 25% s orbital characteristics and 75%. P orbital characteristics. Example: sp³ hybridization of carbon in alkanes.The carbons of Alkanes shows tetrahedral arrangement. The angle between two orbitals is 109-5°.
8.CONJUGATED DIENES
Organic compounds or Hydrocarbons that contain two carbon- carbon double bonds are called Dienes or Diolefin, Dienes occurs ocassionally in nature.
Types of Dienes
Dienes are of three types:1.Conjugated Dienes 2.Cumulated Dienes3.Non-Conjugated Dienes Conjugated Dienes They contain alternate double bonds separated by one single band. CH2=CH-CH=CH2 Cumulated Dienes
In cumulated dienes double bonds are adjacent to each other CH2CH=CH2 Non-Conjugated Dienes
Doube bonds are separated by 2 or more single bonds. CH2=CH-CH2 CH=CH2 9.REARRANGEMENT OF CARBOCATIONS
The shifting of bonding atom or groups in a carbocation for the formation of a more stable carbocation is known as Rearrangement of Carbocations.The shifting can be of two types:1.Hydride Shifting2.Methyl Shifting HYDRIDE SHIFTING
Shifting of hydrogen atom is known as Hydride Shifting.
METHYL SHIFTING
Shifting of methyl group (CHs) is known as Methyl Shift.
10.ELECTROPHILIC ADDITION REACTIONS:
Alkenes are more reactive compare to Alkanes (due to th bond).When an atom or group of atom are simply added to a double bond or triple bond without any substitution or elimination then this type of reaction is known as Electrophilic Addition Reaction.Now addition of an ‘Electrophile’ in an addition reaction is known as Electrophilic Addition Reaction.ExampleCH2CH2 + E-Nu,CH2 CHa 1 E Nu. 1th bond breaks and 20 bond forms during addition reaction.
Mechanism Of Addition Reaction
STEP-I The reagent (E-Nu) like HBr ionizes to give electrophile & nucleophile.STEP-Ⅱ Electrophile (H+) attacks on bond to form a band carbonium ion.STEP-III Addition of Nucleophile on carbonium ion
11.SN1 & SN2 REACTIONS
SN1 SN₂ reactions are nothing but simply a type of Nucleophilic Substitution Reaction. A Nucleophilic substitution reaction is a type of organic reaction in which an atom or group of an atom is replaced from substrate by a nucleophile. The substitution can be occur either in one or two step. The two step mechanism is known as SN Reactions while the one step mechanism is known as SN2 Reactions. Nucleophilic substitution reactions mainly occurs in Alkyl Halides and Alcohols.
TYPES OF NUCLEOPHILIC SUBSTITUTION REACTION
They are of mainly two types 1.SN1 Reaction 2.SN2 Reaction SN1 REACTION
SN1 stands for Unimolecular Nucleophilic Substitution Reaction. It is a two step process. The reaction follows First order kinetics. The reaction takes place in the presence of weak base. Or weak nucleophile. Order of reactivity 30 > 2° 71° STEP-IIt is slow rate determining step in which carbocation is formed. STEP-IIAttack of Nucleophile on carbocation to give product.
SN2 REACTION
SN2 stands for Bimolecular Nucleophilic substitution Reaction.It is a one step process The reaction follows Second Order kinetics. Formation of Transition state takes place. Reactivity order 1° 72°73° MECHANISM OF SN2 REACTION
In SN² reaction the nucleophile attacks on carbon atom of Alkyl halide from backside which results in the formation of transition state e ultimately give product of opposite/inverted configuration to that of initial Alkyl halide.
SN1 REACTION:-
It is a unimolecular Reaction. It follows 1st order kinetics. It is a two step process. Reactivity order: 3072° 71° SN2 REACTION:-
It is a bimolecular Reaction. If follows second order kine.It is a one step process Readivity order: 1072078 FACTORS AFFECTING SN1 & SN
There are following various factors that affect SN’ SN reactions:
Nature Of Alkyl Halide
Reactivity order of Alkyl Halides for SN 3° 72° 71°. Reactivity order of Alkyl Halides for SN2: 1°72°73°.° Nature of Leaving Group
More easily the leaving group removed from carbon atom faster will be substitution reaction. R-I>R-Br >R-CI > R-F Nature of Solvent:
Generally Polar Protic Solvents are used for SN¹ reactions. Polar Aprotic solvents are used for SN reactions.
12.ALDOL & CROSSED ALDOL CONDENSATION
CANNIZARO & CROSSED CANNIZAR
ALDOL CONDENSATION
Aldehydes or ketones having at least one a hydrogen undergoes an organic reaction in presence of dilute base (generally diluk NaOH) to form β-hydroxyaldehyde (also known as Aldol) & the reaction is known as Aldol Reaction. Finally after the formation of Aldol by removing a water molecule a new product form known as Enal e the reaction is known as Aldol Condensation.
Mechanism
STEP-I Hydroxide acts as a base removes the acidic & hydroga from aldehyde.STEP-II Nudeophile attacks on aldehyde at electrophilic carbon atam. STEP-III Removal of Ht from water to form Aldol FINAL STEP
Removal of water molecule from Aldol compound CROSSED
ALDOL CONDENSATION
When aldol condensation is camed out between two different aaldehydes or ketones, then it is known as Crassed Aldal Condensation. Now if only one species will contain a hydrogen then two products will be formed, while. If both the species contain – hydrogen then 4 products will be formed. Lets assume we carried out our reaction blw Formaldehyde (Methanal) & Acetaldehyde (ethanal), Now here acetaldehydı contains a hydrogen while formaldehyou don’t so we get two products by the following reactions CANNIZARO REACTION
Cannizaro reaction is a type of organic reaction in which reaction takes place between those aldehydes that do not contain a hydrogen Reaction takes place only in the presence of concentrated base.
Mechanism
STEP-I Attack of Hydroxide jon (OH-) on aldehyde. Group compound,STEP-II Hydride STEP-III Transfer of proton e addition of Nat CROSSED CANNIZARD REACTION
Crosseel cannizaro is also same as Cannizaro reaction the main difference is here the reaction takes place blw two clifferent dldehyde group not having a hydrogen atom. Reaction takes place in the presence of Concentrated base. The reaction mainly takes place blw formaldehyde f Bangladeshi STEP-I Attack of OH On altered STEP-II Hydride shift STEP-III Transfer of proton e addition of Nat
13.Nucleophilic Addition Reaction of Aldehyde & ketones
Aldehyde e ketones are highly reactive compounds. Both Aldehyde & ketones undergo nucleophilic addition reación because of electrophilic nature of carbon of carbonyl group. As the oxygen atom of both Aldehyde & ketones is more electronegative, therefore it pulls the electron around itself acquring a partial negative charge (S-). Whereas a partial positive charge (St) is developed on carbon atom. The positively charged carbon atom of carbonyl group is then readily attacked by nudeophiles.
Example: Reaction with Hydrogen Cyanide HCN
Aldehyde & ketones undergo a nucleophilic addition reaction with HCN The nucleophile in this reaction is a cyanide ion -CEN Hydrogen Cyanide Acetone Acetone Cyanohydrin Formaldehyde
Uses
It is commonly used as preservatives. It is also used as disinfectants It is used as local anaesthetics. It is used in textile Industry. It serves as building block for synthesis of various chemicals.Benzaldehyde Uses
Benzaldehyde is used as flavouring Agent. It is used in production of various medicines. It is also used in industrial process. It is used as processor for synthesis of various chemicals. Vaniline Uses
Vaniline is used as flavourning agent. It is also used as fregrance in various perfumes. It is used for synthesis of vanous medications. It is also used in various cosmetics.
17.ACETIC ACID,CITRIC ACID,SALICYLIC ACID, BENZOIC ACID,ETHYLENE Diameter, AMPHETAMINE
1.
Acetic Acid
-CH3-COOH UsesIt is widely used in food industry.It serves as precursor for synthesis of various chemicals.It is also used as deansing agent.It is used as preservatives.2.
Citric Acid
Uses It is used as flavour enhancer. It is used as cleansing agent. It is used in cosmetic Industry. Also usecl in various medications. 3.
Salicylic Acid
Uses-Precursor of aspirin. In various cosmetic products. As plant hormone. For acne treatment. 4.
BENZOIC ACID
Uses-As preservahves. In cosmetics. As antiseptics. 5.
Ethylene Diamene
Uses-Formulahon of fertilizers. Used in vanbus pharmaceuhtals. Synthesis of various Chemicals. 6.Amphetamine Uses-Apehile supresant performance enhancer
14.CARBOXYLIC ACIDs
Carboxylic Acid is an organic compound that contains a Carboxyl group (-COOH). This group consist of a carbonyl group (C=0) alttached to hydroxyl group (-он). They can be either aliphatic or aromatic.
ACIDITY OF CARBOXYLIC ACIDS
Carboxylic acids are Acidic in nature. The acidity of carboxylic acids refers to theier ability to donate a proton (H+) foom the carboxyl group (-COOH) to form a Carboxylate ion (-coo-). When carboxylic acids dissociate in water, they form Carboxylate ion & hydronium ion by donating Hr to the water. Now this carboxylate ion becomes very stable due to two major key factors:1.Resonance stabilization 2.Electronegative Oxygen Atoms Resonance Stabilization
When a carboxylic add loses a proton (H+), it forms a carboxylate ion CR-coo-) This anion is stabilized by resonance, as negative charge can be delocalized between the two oxygen atoms. This delegation lowers the energy of car carboxylate ion making it more stable thus making loss of proton more favourable Electronegative Oxygen Atoms
The two oxygen atoms in carboxyl group are highly electronegahve They pull electron density away from hydrogen in -OH group making it easier for proton to leave e dissociate, Now these electronegative oxygen atoms stabilizes the negative charge on carboxylate ion.Also the pka value of carboxylic acids are very less ie., 4-5 indicating it as a strong acid compare to Alcohols e many other organic acids.
EFFECT OF SUBSTITUENTS ON ACIDITY OF CARBOXYLIC ACIDS
There are mainly two types of substituents that generally shows their effect on acidity of carboxylic acids:1.Electron Withdrawing Group 2.Electron Releasing Group Electron Withdrawing Group
Election withdrawing groups increases the addity of carboxylic acids because EWGs stabilizes the negative charge on the Carboxylate ion through Inclucive of resonance effect. In a carboxylic acid, the electron withdrawing groups pull electron density away from carboxylive group. This makes carboxylate ion more stable and thus making Carboxylic acid more acidic Effect of Electron Releasing Group
Electron Releasing Groups (ERGs) decreases the acidity of carboxylic aads This is because ERGs Increases electron density to the
15.BASICITY OF ALIPHATIC AMINES
Aliphatic amines are organic compounds that contains an amino group (-NH2) attached to an aliphant carbon chain. I can also be defined as aliphatic derivatives of Ammonici (NH3) in which 1 or more hydrogen atom of amania i’s replaced by alkye groups.
Classification of Aliphatic Amines
Aliphatic Amines are classified as Primary, Secondary or Tertiary depending upon whether 1, 2 or all 3 atoms of hydrogen have been replaced by Alkye Groups 1.Primary Aliphatic Amines (NH2CH3) 2.Secondary Aliphatic Amines (NH (CH₃)₂) 3.Tertiary Aliphatic Amines (N(CH₃)₃) Basicity Of Aliphatic Amines Basicity Of Aliphatic Amines
Aliphatic amines are basic in nature. The basicily of aliphatic amines refers to their ability to Cccept protons CHlons) from acids, which is a measure of their strength as boses. Also they have the ability to donate their lone pair of electrons present on nitrogen atom. R-NH2 + H2O R-NH + OH-
Factors Influencing, basicity of Aliphatic Amines
Several factors influences basicity of aliphatic amines: 1.Alkyl Groups Alkyl Groups attached to the nitrogen atom increases its electron density, enhancing its ability to donate lone pair of electrons thus increasing basicity.
Steric Effects
In tertiary amines, steric hindrance can reduce the auxilibility of lone pair, potentially decreasing its ability compared to primary & secondary amines.
Hybridization
In aliphatic amines, there is sps hydbridization compared to aromatic amines (spa) making stronger base than other amind.
Order of basicity of Aliphatic Amines
2° Amines >3º Amines >1° Amines >Ammonia 2° Amines have greatre basicity compared to 3º Amines because of sternic hindrance affect.
EFFECT OF SUBSTITUENTS ON BASICITY OF AUPHATIC AMINES
1.
Effect of Electron Releasing Groups
Electron Releasing Groups increases the electron density on Aromatic Amines Aliphatic Amines, hence they tends to increases the basicity of aliphatic amines. Example: -CH3. -OH etc.
Effect of Election Withdrawing Groups
Electron withdrawing Groups due to their high electronegativity decreases electron density on nitrogen atom, reducing is ability to accept protons & thus decreases basty. Example: -CH₃,-OH etc.
16.CARBOXYLIC ACIDS,AMIDES,ESTERS
INDUCTIVE EFFECT
The partial shift / displacement of electrons from a less electronegative atom towards a more electronegative atom is known as Inductive effect. Now this inductive effect is of two types: 1.Positive Inductive Effect (+1) 2.Negative Induchve Effect (-1)
+I Effect
This effect occurs when a substituent or group in a molecule increases electron density to the rest of the molecule. Basically this effect is shown by Electron Releasing Groups. Example: Alkyl Groups (Methyl, Ethyl).
-I Effect
This effect occurs when a substituents or group in a molecule decreases electron density to the rest of the molecular. Basically, this effed is shown by Electron Withdrawing Groups. Example: Halogens (CI, Br).
QUALITATIVE TEST FOR CARBOXYис ACIDS
Litmus Test
Place a drop of solution of carboxylic acid sample on a blue litmus paper. If blue litmus turns red, it indicates the presence of acid Sodium Bicarbonate Test
Carboxylic acids reacts with sodium bicarbonate to produce Salt of carboxylic acid along with effervescence of CO2 Ester Formation Test
On healing carboxylic acids with an alcohol in presence of small amount of sulphuric acid, a fruity smell of Ester is obtained. RCOOH + R’OH RCOOR’ + H2O Conc.
QUALITATIVE TEST FOR ESTERS
1.
Hydroxamic Acid Test
Esters upon reaction with hydroxylamine yeild’s hydroxamic acid, which upon treatment with ferric chloride forms Ferric hydroxamate complex with Bluish red/ violet colour. R-Coo-R’ + NH2OH →R-CONHOH + R-OH Fecl3 (RCONHO) Fe + H+ (Bluish Red Complex) 2.
Hydrolysis Test
Alkaline hydrolysis of esters Converts esters into acid salt and alkohol. ROOOR NOCH RCOONa + R’OH 1.
QUALITATIVE TEST FOR AMIDE
Alkali Test
Simple primary amide can be decomposed by boiling with Alkali and thereby evoluing, ammonia 0 CH3-C-NH2 + NaOH CH₃CO2Na + NH3 2.
Biuret Test
When aliphatic diamide is heated at temperature above its melting point, ammonia is evolved, this biuret in alkali medium gives violet colour with a drop of copper sulphat solution. 0 2 NH2-C NH2 NH2 NHC NH + NH3-CuSO4Violet colour complex