1. PHYSICO-CHEMICAL PROPERTIES OF ORGANIC COMPOUNDS

2. 1. Solubility of organic compounds -the balance of -polar and apolar (hydrophilic and hydrophobic) molecule parts: Hydrophobic: no possibility for H-bond formation Hydrophilic: H-bond formation is possible

3. 1. alkyl (alkane, alkene, alkyne), aryl (aromatic) borrows hydrophobic character -they are non-polar structures -their interactions are hydrophobic Solubility of organic compounds 2. oxi (alcohol), oxo (ketone, aldehyde, ether) - substituents borrow weak hydrophilic character

4. Solubility of organic compounds 3. ester, amide, nitro substituents borrow constant, hydrophilic character 4. amine and carboxylic substituents borrow hydrophilic character of variable strength the pH dependence of amine and carboxylic acid ionisation is a solubility switch (buffering effect of proteins)

5. Solubility of organic compounds Carboxylic acid, amine Alcohol Aldehydes, ketones, halogen groups, ethers Alkyl group Increasing solubility

6. Isomerisms 1.Functional isomerism - Same formula, different function groups - different chemical properties 2. Geometric isomerism: e.g. cis-trans, optical

7. 2. Geomtrical isomerism Optical isomerism or chirality -Special 3D arrangement of atoms -Central concept: -An optically active substance is one which can rotate The plane polarized light

8. Optical isomerism or chirality What is the plane polarized light???? - The light in that case electromagnetic light is always a mixture of waves -and each waves vibrates in every direction of space Non-polarized Incident light Plane polarized reflected light

9. Optical isomerism or chirality The reflected light contains only one direction vibrating light It’s called plane polarized light

10. Optical isomerism or chirality How we can measure the degree and the direction of rotation of plane polar light In case of the optically active organic compounds??

11. Optical isomerism or chirality So, optical activity means the ability to rotate the plane polarized light It is caracterized by the degree and the direction of rotation We can distinguish + and – direction + direction is called : clockwise - Direction is called: counterclockwise

12. Optical isomerism or chirality Why can atoms do that??? Optical active carbon atom: The carbon atom is in sp3 hybride state the carbon atom has 4 differet substituents – asymmetric carbon atom!!! Symmetric carbon atom 2 substituents are the same Asymmetric carbon ( C* ) – 4 different substituents

13. Optical isomerism or chirality Optically active molecules ( asymmetric carbon) They are optical isomers The 2 isomers can’t be converted to each other, only by chemical reaction, Only by breaking bonds and making new ones They are mirror image counter parts of each other The chemical and the physical properties of the optical isomers are the same, they are different only by the direction of plane polarized light rotation

14. Optical isomerism or chirality Optical isomers: -Rotate the plane polarized light to the same degree but in different direction -One in – other one in + direction -When 2 optical isomers are in 1:1 ratio in a solution ( mixture) it is called -Racemic mixture -That’s why in racemic mixture we can’t detect any rotation of light because they cancel each other

15. Optical isomerism or chirality Optical isomerism also called handedness and the Asymmetric carbon atom ( C* ) – optically active – is also called as chiral carbon The arrangement of the substituents around the C atom is called configuration

16. Optical isomerism or chirality Optical isomers: glyceraldehyde It was the first discovered as an optically active compound (+) glyceraldehyde d- glyceraldehyde (-) glyceraldehyde l- glyceraldehyde agreement

17. Optical isomers: Optical isomerism or chirality They said: glyceraldehyde is the absolute reference Not only the glyceraldehyde but other organic compounds are Optically active too e.g. amino acids, hydrocarbons.. They converted the structures of all these compounds to glyceraldehyde e.g. if the configuration of an amino acid(AA) is converted to the configuration of (+) or d- glyceraldehyde, the the AA is (+ ) or (d) configuration as well

18. Optical isomers: Optical isomerism or chirality Lower case d and l are relative configurations : relative to glyceraldehyde Later they proved that the (+) rotation of the plane polarized light of the glyceraldehyde is really the d-configuration of glyceraldehyde !!! D and L are the absolute configurations !!! - ( if we know the true configuration we use capital D and L) Because the d- and l - configuration of glyceraldehyde are correct everything became D and L configuration

19. Optical isomers: Optical isomerism or chirality In the nature all of the amino acids are in L- configuration all of the carbohydrates are in D- configuration DL D-glucose

20. Optical isomers: Optical isomerism or chirality Let’s see some exapmples: 2,3-dihydroxybutanedioic acid Going around rule: we have to start to draw the direction of the rotation from the most reactive substituent e.g. -COOH more reactive than the -H *

21. Optical isomers: Optical isomerism or chirality Diasteromers: partial mirror image counterparts Enantiomers: complete mirror image counterparts When there are more than 1 chiral carbon atom in one compound you can calculate the number of the isomeric forms of this given compound: 2 n where n is the number of the asymmetric (chiral carbon atoms)