HL Option G Organic Chemistry

1. HL Option G Organic Chemistry

2. IB HL Option Objective • G.9.1 Describe, using equations, the reactions of acid anhydrides with nucleophiles to form carboxylic aicds, esters, amides and substituted amides. • Include the nucleophiles: water, alcohols, ammonia and amines.

3. G.9.1 Describe, using equations, the reactions of acid anhydrides with nucleophiles to form carboxylic aicds, esters, amides and substituted amides. Acid Anhydrides Ethanoic anhydride • Acid Anhydrides are often used in organic synthesis reactions because they are more reactive than a carboxylic acid. The –OCOR group is a better leaving group than an –OH group.

4. G.9.1 Describe, using equations, the reactions of acid anhydrides with nucleophiles to form carboxylic aicds, esters, amides and substituted amides. Acid Anhydride with Water Can react with water to go back to two ethanoic acids. + H2O 2

5. G.9.1 Describe, using equations, the reactions of acid anhydrides with nucleophiles to form carboxylic aicds, esters, amides and substituted amides. Acid Anhydride with Alcohol Can react with ethanol to form an ester. + + CH3COOH What common drug can be made in this reaction from salicylic acid?

6. G.9.1 Describe, using equations, the reactions of acid anhydrides with nucleophiles to form carboxylic aicds, esters, amides and substituted amides. Acid Anhydride with Ammonia Can react with ammonia to form an amide. + NH3 + CH3COOH

7. G.9.1 Describe, using equations, the reactions of acid anhydrides with nucleophiles to form carboxylic aicds, esters, amides and substituted amides. Acid Anhydride with Amines Can react with amines to form secondary amides. + + CH3COOH What is the common name of the structure on the right, and what is it used for?

8. IB HL Option Objective • G.9.2 Describe, using equations, the reactions of acyl chlorides with nucleophiles to form carboxylic acids, esters, amides and substituted amides. • Include the nucleophiles: water, alcohols, ammonia and amines.

9. G.9.2 Describe, using equations, the reactions of acyl chlorides with nucleophiles to form carboxylic acids, esters, amides and substituted amides. Acyl Chlorides Ethanoyl chloride • The chloride makes an even better leaving group than acid anhydride. It is more reactive.

10. G.9.2 Describe, using equations, the reactions of acyl chlorides with nucleophiles to form carboxylic acids, esters, amides and substituted amides. Acyl Chloride with water + H2O → + HCl Notice how instead of the other product being ethanoic acid, it is now HCl. This will be the same throughout.

11. G.9.2 Describe, using equations, the reactions of acyl chlorides with nucleophiles to form carboxylic acids, esters, amides and substituted amides. Acyl Chloride with alcohol + Notice a trend here? How does this compare to the products from the acid anhydride?

12. G.9.2 Describe, using equations, the reactions of acyl chlorides with nucleophiles to form carboxylic acids, esters, amides and substituted amides. Acyl Chloride with alcohol Can you predict the products for the reactions with ammonia and ethanamine?

13. IB HL Option Objective • G.9.3 Explain the reaction of acyl chlorides with nucleophiles in terms of addition-elimination mechanism. • Check out the mechanism in your study guide. Draw the mechanism with curly arrows on a sheet of paper!

14. IB HL Option Objective • G.10.1 Describe, using equations, the nitration, chlorination, alkylation and acylation of benzene. • Include the use of for the benzene ring as well as formulas such as C6H5NO2. • The introduction of more than one group into the benzene ring will not be assessed here.

15. G.10.1 Describe, using equations, the nitration, chlorination, alkylation and acylation of benzene. • Benzene has a high electron density due to the presence of delocalized pi electrons. • This makes benzene susceptible to electrophilic attack. • However, benzene does not readily undergo addition reactions, since addition would disrupt the stability of the delocalized pi bonds. • Therefore, reactions with benzene undergo electrophilicsubstitution reactions.

16. G.10.1 Describe, using equations, the nitration, chlorination, alkylation and acylation of benzene. • Benzene reacts with nitric acid and concentrated sulfuric acid at 50̊C. • This reaction creates nitrobenzene. Write the equation for this reaction along with byproducts.

17. IB HL Option Objective • G.10.2 Describe and explain the mechanisms for the nitration, chlorination, alkylation and acylation of benzene. • Include the formation of NO2+ from the reaction between concentrated nitric and sulfuric acids, and the formation of Cl+, R+, and RCO+ from reactions involving aluminum chloride as a halogen carrier catalyst.

18. G.10.2 Describe and explain the mechanisms for the nitration, chlorination, alkylation and acylation of benzene. Nitrobenzene • In the reaction of nitric acid with benzene to produce nitrobenzene, sulphuric acid acts as a catalyst. • Sulphuric acid protonates the nitric acid which produces water. • The nitronium ion (NO2+) then attacks the benzene. In order to regain the stability of the delocalized electrons, the hydrogen leaves which regenerates the catalyst.

19. G.10.1 Describe, using equations, the nitration, chlorination, alkylation and acylation of benzene. G.10.2 Describe and explain the mechanisms for the nitration, chlorination, alkylation and acylation of benzene. Chlorination • In order for benzene to undergo addition with chlorine, a halogen carrier, aluminum chloride (AlCl3), is needed as a catalyst. • Aluminum chloride can act as a Lewis acid (electron acceptor) since there are only six electrons around the aluminum atom. • Aluminum chloride will attract a Cl- from the chlorine (Cl2), and you now have a Cl+ ion (strong electrophile). • After Cl+ attacks, the hydrogen is released, which creates HCl, regenerating the catalyst.

20. G.10.1 Describe, using equations, the nitration, chlorination, alkylation and acylation of benzene. G.10.2 Describe and explain the mechanisms for the nitration, chlorination, alkylation and acylation of benzene. Friedel-Crafts Reactions • Friedel-Crafts reactions are using halogen carriers (AlCl3), reacting them with halogenated organic compounds (C2H5Cl), to create electrophilic chains (R+ and RCO+). These alkyl and acyl groups are then substituted into the benzene ring. • Use equations and show the mechanism for when benzene reacts with chloroethane. Show the products.

21. G.10.1 Describe, using equations, the nitration, chlorination, alkylation and acylation of benzene. G.10.2 Describe and explain the mechanisms for the nitration, chlorination, alkylation and acylation of benzene. Acylation • Remember ethanoyl chloride? Show the reaction of ethanoyl chloride and benzene using aluminum chloride as a catalyst to form phenylethanone.

22. IB HL Option Objective • G.10.3 Describe, using equations, the nitration, chlorination, alkylation and acylation of methylbenzene. • G.10.4 Describe and explain the directing effects and relative rates of reaction of different substituents on a benzene ring.

23. G.10.4 Describe and explain the directing effects and relative rates of reaction of different substituents on a benzene ring. • The methyl group in methylbenzene has a positive inductive effect (i.e. it pushes electrons towards the ring rather than pulling electrons from it). • Methylbenzene is thus more reactive to electrophiles, and CH3 is known as an activating group. • NO2, as learned earlier, pulls electrons towards it, and decreases the reactivity of benzene. Thus, NO2 is an example of a deactivating group.

24. G.10.3 Describe, using equations, the nitration, chlorination, alkylation and acylation of methylbenzene. • The methyl group on methylbenzene is like a director…. • It directs the electrophiles to the 2 or 4 position on the benzene ring. • Therefore, if chlorine reacts with methylbenzene, only 2-chloromethylbenzene and 4-chloromethylbenzene are formed. This is due to the positive inductive effect of the CH3 group making a 2 or 4 intermediate more energetically stable. • This will be true for all substituentsto methylbenzene (NO2, Cl, R, and CO-R)

25. G.10.4 Describe and explain the directing effects and relative rates of reaction of different substituents on a benzene ring. -OH group • Even though oxygen is electronegative here, it actually partially donates a non-bonded pair of electrons to the benzene ring, making it more reactive. • At room temperature, phenol will rapidly react with aqueous chlorine to produce 2,4,6-trichlorophenol (notice the locations of the chlorines).

26. G.10.4 Describe and explain the directing effects and relative rates of reaction of different substituents on a benzene ring. NO2 group • NO2, as mentioned earlier, is electron withdrawing, so it is deactivating (it does not have a non-bonding pair on the nitrogen to partially donate). • Therefore, it will not be directed to the 2,4 spots, but instead the 3 spot. • For those of you who were here, we performed a lab where we added nitrobenzene with concentrated nitric acid and refluxed for a while with concentrated sulfuric acid to produce 1,3-dinitrobenzene.