all organic reagents and their functioning for jee and neet

 

organic important topics for jee

 

jee important topics to revision inorganic and physical chemistry

 

Acidic and Basic strength in different cases complete information goc

 

Acidic and Basic strength in different cases complete information

TYPE 1.

p-Nitrophenol > p-Chlorophenol >  phenol > p-Cresol > p-Methoxy phenol

p-NitroBenzoic acid > p-ChloroBenzoic acid >  Benzoic acid > p-Toluic acid > p-Methoxy Benzoic acid

p-NitroAniline < p-ChloroAniline <  Aniline < p-Toluidine < p-MethoxyAniline 

TYPE 2…

o-BromoPhenol  > m-BromoPhenol > p-BromoPhenol  >  Phenol [10]

o-ChloroPhenol  [8.48] > m-ChloroPhenol [9.02] > p-ChloroPhenol [9.38]>  Phenol

o-FluoroPhenol  [8.81] > m-FluoroPhenol [9.28] > p-ChloroPhenol [9.95]>  Phenol

o-Bromobenzoic acid [3.1] > m-BromoBenzoic acid [3.93]> p-BromoBenzoic acid [4.1] >  Benzoic acid [4.17]

o-ChloroBenzoic acid [2.89]  > m-ChloroBenzoic acid [3.82]> p-ChloroBenzoic acid [3.98]>  Benzoic acid [4.17]

p-ChloroPhenol [9.38] > p-FluoroPhenol [9.95] > p-BromoPhenol > p-IodoPhenol > Phenol

p-ChloroBenzoic acid [3.98] > p-FluoroBenzoic acid [4.14] > p-BromoBenzoic acid [4.1] > p-IodoBenzoic acid > Benzoic acid

o-Bromoaniline [11.4] < m-Bromoaniline [10.49] < p-Bromoaniline [10.09] < Aniline 

TYPE 3….

Phenol > m-Cresol [10.08]  > p-Cresol [10.14] > o-Cresol [10.28]

O-Toluic acid [3.89] > Benzoic acid [4.17]> m-Toluic acid [4.28] > p-Toluic acid [4.35]

O-Toluidine < Aniline  < m-Toluidine  < p-Toluidine

TYPE 4…

m-Methoxyphenol [9.65]  > Phenol  > o-Methoxyphenol [9.98] > p-Methoxyphenol [10.21]

m-HydroxyPhenol (Benzene-1,3-diol) [9.44] > o-Hydroxyphenol (Benzene-1,2-diol) [9.48] > p-Hydroxyphenol (Benzene-1,4-diol) [9.96] > Phenol [10]

o-Methoxybenzoic acid = m- Methoxybenzoic acid > Benzoic acid  > p-Methoxybenzoic acid

2,6-diHydroxybenzoic acid [2.3] > o-HydroxyBenzoic acid [2.98] > m-HydroxyBenzoic acid [4.08] > Benzoic acid > p-HydroxyBenzoic acid [4.58]

p-Methoxyaniline > Aniline > o-MethoxyAniline > m-Methoxyaniline [o-isomer should be weakest due to Ortho effect, but in meta-isomer, there is only –I effect hence it becomes weakest base]

TYPE 5…..

p- NitroPhenol [7.15] > o-Nitrophenol [7.23] > m-Nitrophenol [8.40] > Phenol
[o-isomer must be strongest acid, but due to chelation (intramolecular H-bonding) b/w  adjacent–OH & – NO2, deprotonation becomes slightly difficult.]

o-NitroBenzoic acid > p-NitroBenzoic acid > m-NitroBenzoic acid > Benzoic acid

o-Nitroaniline < p-Nitroaniline  < m-Nitroaniline < Aniline

TYPE 6…..

0-Aminophenol [9.71] > m-Aminophenol [9.87] > Phenol > p-Aminophenol[10.3]

Benzoic acid [4.17] > m-Aminobenzoic acid [4.79] > p-AminoBenzoic acid [4.92] > o-Aminobenzoic acid (Anthranilic acid) [4.98]

TYPE 7..[HYDROGEN BONDING]

pKa1 (phthalic acid or Benzene-1,2-dicarboxylic acid) < pKa1(Terephthalic acid or Benzene-1,4-dicarboxylic acid) < pKa1 (Isophthalic acid or Benzene-1,3-dicarboxylic acid)

pKa1 (maleic acid) < pKa1(fumaric acid); pKa2 (maleic acid) > pKa2(fumaric acid)

TYPE 8..[SIR EFFECT]

2,6-diMethylbenzoic acid [3.21] > 2-t-ButylBenzoic acid [3.46] > o-Toluic acid [3.91]

3,5-diMethyl-4-CyanoPhenol > 2,6-diMethyl-4-CyanoPhenol   ;
[Here, “NO” SIR effect as Cyano is a linear group so, second is less acidic due to closeness of both methyl group to –OH hence greater +I decreases acidic character.]

2,6-diMethyl-4-NitroPhenol >  3,5-diMethyl-4-NitroPhenol
[In second, due to SIR effect,  Nitro group goes out of plane & hence unable to withdraw electron by –R effect.]

2,4-diNitroBenzoic acid > 2-NitroBenzoic acid > 3,5-diNitroBenzoic acid

TYPE 9..[GENERAL ORDER]

RCO2H > RCO3H (peroxycarboxylic acids)

RSO3H > RCOOH > H2CO3 [6.3] > C6H5OH [10] > CH3OH [15.5] > H2O [15.7]> ROH > RC#CH > NH3 > RCH=CH2 > RCH3 > H2

RSH >ROH

TYPE 10..[GENERAL EXCEPTIONS]

Formic acid [3.75] > Benzoic acid [4.17] > Acetic acid [4.74] [IIT 85]

C6H5-CH2-CO-OH > CH2=CH-CH2-CO-OH

CH#C-CO-OH >  CH2=CH-CO-OH > CH3CH2COOH

CH#C-CH2-CO-OH [3.22] >  CH2=CH-CH2-CO-OH [4.35]

TYPE 11..(GASEOUS PHASE/FIELD EFFECT)

t-BUTANOL > n-BUTANOL

PROPANOIC ACID > ACETIC ACID

TYPE 12..[GENERAL]

pKa value of CF3-CO-OH is zero (0.18) & it is the strongest organic acid known.[(10^5 times stronger than acetic acid.]

Formic acid is 10 times stronger than Acetic Acid.

N3H [2.810^(-5)] > CH3COOH [1.810^(-5)]

Beta-KETOESTERS are stronger acids than Alcohols & Esters.

NC-CH2-CO-OH > CH3-CO-CH2-CO-OH

CH3COOH > HO-CH2=CH2-OH > HO-OH > CH3CH2OH [IIT-80]

OXIMES(>C=N-OH) > HYDROXYL AMINE (NH2OH)

TYPE 14..[ACID-BASE REACTIONS]

Acid-base equilibriums move towards formation of weaker acids & weaker bases.

2,4,6-triNitroPhenol or Picric acid  [0.38] does dissolve in aq NaHCO3

Carboxylic acids dissolves in aq NaHCO3 whereas Phenol does not.

4-ChloroPhenol dissolves in NaOH (aq.) whereas 4-Chloro-1-methylBenzene does not.

·         Electron releasing groups (ERG) increase e- density of bases or stabilises “cationic conjugate acids” & hence increase basic character.

·         EWG increase stabilisation of “anionic” conjugate bases & hence increase acidic character.

·         Acidic Character is proportional to Stability of corresponding conjugate base.

·         Basic Character is proportional to Stability of corresponding conjugate acid.

·         Inductive effect operates from ortho as well as meta & para-positions & inductive effect is strongest from ortho position (being nearest).

·         Resonance or mesomeric effect does not affect from groups attached at meta positions. However it does affect from both ortho and para-positions with equal intensity.

·         Alkyl groups exert release e- by hyperconjugation effect (+H) from ortho & para-positions.

·         The groups having lone pair at the key atom (e,g -OH, -OR, -O-CO-R, -NH2, -NHR, NR2, -NH-CO-R, -X etc.) exert +R effect(release e- by resonance) when conjugated (alternate or attached) to unsaturated system like aromatic ring e,g, Benzene ring.

·         Order of +R effect: -NH2 > -OR > -OH >-OCH3 > -OCOR > -F > -Cl

·         CH3OH is slightly stronger acid than water hence -OCH3 is slightly more e- donating than -OH.

·         For -Cl, -Br & -I , +R effect is almost ineffective due to poor overlap of 2p orbital of Carbon with 3p or 4p or 5p of Cl, Br or I.

·         The groups having Key atom multiply bonded to more powerful electronegative atoms (e.g -NO2, -CN, -CHO, -CO-R, -COCl, -CONH2, -CO-O-COR, -CO-OR, etc) exert -R  effect (withdraw e- by resonance) when conjugated (alternate or attached) to unsaturated system like aromatic ring e,g, Benzene ring.

·         Due to ortho effect, in most cases,-

·         “Ortho-isomer of Benzoic acid is strongest Acid as compared to Simple benzoic acid or meta & para-isomers  & Ortho- isomer of Aniline is Weakest Base as compared to Simple Aniline or meta & para-isomers.”