ORGANIC BASES

Organic bases are different from general bases here is all details about organic bases . Their strength and factors affecting their strength. We also discuss its applications. We will also upload organic acids and their strength very soon.

1. PRESENTATION OF CHEMISTRY TOPIC: ORGANIC ACIDS AND BASES PREPARED BY: AZIZ KHAN PRESENTERS: AZIZ KHAN SUBHAN ULLAH HAQ NAWAZ UMER FAROOQ ZEENAB AIMAN

2. ORGANIC BASES WHAT ARE ORGANIC BASES? Organic bases are organic compounds which acts as a base. Organic bases are usually but not always proton acceptors amines and hydrogen containing heterocyclic compounds are organic bases. EXAMPLE: Pyridine , methyl amine etc

3. PYRIDINE AND METHYL AMINE PYRIDINE METHYL AMINE

4. Some organic bases are hydroxide donors TETRAMETHYL AMONIUM HYDROXIDE

5. PROPERTIES OF ORGANIC BASES Usually proton acceptor. CH 3 NH 2 +H 2 O CH 3 NH 3 + OH - 2. Some are Hydroxide donors. Example: Tetra methyl ammonium hydroxide (explained above) 3. They are generally weak bases.

6. Other properties are similar to that of inorganic bases. 3. They have a ph of more than 7. 4. They have a soapy feel. 5. They have a bitter taste. 6. They are corrosive to human tissue. 7. They react with acid to form salt and water.

7. FACTORS AFFECTING STRENGTH OF ORGANIC ACIDS 1. STABILITY OF ANION: Acidity is directly proportional to stability of anion. When the anion will be more stable it will not react in the backward direction and hence more H + ions will produce. For example : which one is more acidic. a. HCOOH b. CH 3 COOH The anion of HCOOH is more stable than CH3COOH because CH3COOH have positive inductive effect.

8. EXPLANATION HCOOH HCOO - + H + ANION: HCOO- Stable because no inductive effect. CH3COOH CH3COO - + H + anion is not stable due to positive inductive effect. + INDUCTIVE EFFECT

9. ELECTRONEGATIVITY Electronegativity is directly proportional to acidic strength. Increasing the number of electronegative atoms or groups on atom decreases the electron density in the acidic bond, making the loss of the proton easier.  For example: in H X the X attract electron pair towards itself and hence decreasing the strength of HX bond and hence it will easily donate H+. So it is a strong acid.

10. ACIDITY TREND

11. HYBRIDIZATION As we know that SP3 is less electronegative than SP2 and SP2 is less electronegative than SP so acidity order will be. SP>SP2>SP3 So the acidity order of the following Compound will be. CH3CH2COOH<CH2 CHCOOH<CH C COOH SP3 SP2 SP

12. INDUCTIVE EFFECT Positive inductive effect is inversely proportional to acidity while negative inductive effect is directly proportional to acidic strength . Because in + inductive effect one atom destabilize an anion by giving it an electron. While in – inductive effect an atom stabilize anion by withdrawing electron from it.

13. EXPLANATION a. CH3 CH3COOH b. CH2CH3COOH c. FCH3COOH The acidity order will be a<b<c c is more acidic because of negative inductive effect b is less acidic because of single positive inductive effect and a is very less acidic because of double positive inductive effect. CH3

14. RESONANCE In resonance the formal charge and the unpaired electron is shared by more than two nuclei hence stabilizing the compound. For example: a. ROH b. COOH b is more acidic than a because of resonance. ROH H + + R O - RCOOH

15. AROMATICITY A compound which become aromatic after donating proton will be more acidic. FOR EXAMPLE: NaNH 2 _

16. FACTORS AFFECTING STRENGTH OF ORGANIC BASES AVAILABILITY OF LONE PAIR : Most of the organic bases are Lewis bases and we all know that Lewis bases are those bases which donate lone pair of electron. N H H R H + RNH 3

17. CHARGE One definition of a base is to accept proton . More negative charge means more probability to accept proton. EXAMPLE: a. A + b. B c. C - d. D -2 NOT BASIC NEUTRAL BASIC MORE BASIC

18. ELECTRONEGATIVITY When an atom have greater electronegativity it means that the atom is greedier for electrons. It is less willing to share its electron pair. So it is less basic. Electronegativity is inversely proportional to basicity. EXAMPLE: a. CH3 N CH3 b. CH3CH2 CH3 F N is less electronegative and hence more basic F is more electronegative and hence less basic.

19. HYBRIDIZATION The order of basicity in hybridization will be SP3 > SP2 > SP In SP3 hybridization the hybridized orbital is form from three orbitals and hence have greater size and less electronegativity and are more basic while SP2 and SP have relatively smaller size and hence greater electronegativity and they are less basic.

20. EXPLANATION a. b. N N H It is less basic because of SP2 hybridization(high electronegativity) It is more basic because of SP3 hybridization(low electronegativity)

21. ATOMIC SIZE Size is inversely proportional to basicity. Atoms with smaller atomic size will have greater electron density increasing basicity while atoms with larger atomic size will have less electron density reducing basicity. EXAMPLE: a. CH 3 Br b. CH 3 CH 2 CO 2 - It is less basic due to the greater size of Br It is more basic due to the smaller size of O

22. EXPLANATION Br O Br have large size and small electron density and is difficult for acceptor to attack hence less basic. O have small size and greater electron density and it is very easy for acceptor to attack and hence more basic.

23. INDUCTIVE EFFECT When atom in a molecule give or take electron from atom donating electron or proton it is known as inductive effect. It has two types . POSITIVE INDUCTIVE EFFECT: When an atom give electron to a donating atom. NEGATIVE INDUCTIVE EFFECT: When an atom withdraw an electron from donating atom.

24. EXPLANATION Positive inductive effect is directly proportional to basicity while negative inductive effect is inversely proportional to basicity. EXAMPLE: a. CH 3 N H b. NO 2 N CH 3 H CH 3 It is basic due to positive inductive effect It is less basic due to negative inductive effect

25. ORDER FOR BASICITY OF AMINES PRIMARY AMINES < SECONDARY AMINES > TERTIARY AMINES Primary amines have single + inductive effect That is why it is less basic while secondary carbon have double + inductive effect that is why it is more basic while tertiary have triple inductive effect but it is completely cover by groups which allow very little contact of donor and acceptor and hence are less acidic.

26. TRAGIC CHANGE IN AMINES BASICITY a. CH 3 NH 2 b. CH 3 NH CH 3 c. CH 3 N CH 3 CH 3 Single positive inductive effect less basic. Double positive inductive effect more basic. Less contact of donor and acceptor less basic.

27. RESONANCE Resonance is inversely proportional to basicity because resonance decrease electron density delocalizing the charge as will as the electrons hence decreasing the basicity. CH 3 NH CH 3 ELECTRON DENSITY NH 2 ELECTRON DENSITY

28. RESONANCE IN BENZENE

29. EXPLANATION In resonance the electrons are busy in delocalization and are not available for donation hence decreasing basicity.

30. NO EFFECT OF RESONANCE Some time resonance have no effect on basicity. EXAMPLE: C O - H H RESONANCE

31. BUT IN THIS CASE IT WILL EFFECT CH 3 CH 2 CO 2 - C C C H H H H H O & - O & - RESONANCE

32. APPLICATION OF ORGANIC BASES 1. Pyridine is used as a versatile solvent. Deuterated pyridine (pyridine-d 5 ) is a common solvent for HNMR spectroscopy. 2. pyridine- borane C 5 H 5 NBH 3 (M.P 1O-11C) is a mild reducing agent with improved stability compared to sodium boro hydride (NaBH4) in protic solvents and approved solubility in aprotic organic solvent.

33. 3. Pyridine is used as a denaturant for anti freeze mixtures. 4. Pyridine is sometimes used as a ligand in coordination chemistry. 5. Imidazole has been used extensively as a corrosion inhibitor on a certain metals like copper. 6. Imidazole can also be found in various compounds that are used for photography and electronics. 7. The thermo stable polybenzimidazole contain imidazole fused to a benzene ring and act as a fire retardant.

34. 8. Methyl amines is used to make intermediates for wide range of agriculture chemicals including herbicides, fungicides, insecticides, biocides and miticides. 9. Alkynealkanolamines have a large use in the treatment of natural gas and oil. 10. P- methylaminophenol sulfate Used as a photographic developer. 11. Methyl amines are also used As an animal nutrients , catalyst , electronics and explosives. 12. Benzemedazoles are often bioactive.

35. Many anthelmintic drugs (albandazol , mebendazole , triclabendazole , belongs to the benzimedazole class of compound. 13. Benzimedazole also binds to the spindle microtubules and blocks nuclear division. 14. Benzimedazole is also used in several dyes.

36. BY AZIZ KHAN