6.1 AROMATIC COMPOUNDS AND CARBONYLS Flashcards Preview

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Flashcards in 6.1 AROMATIC COMPOUNDS AND CARBONYLS Deck (10)
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Benzene


- has the formula C6H6


- has a cyclic structure, with its 6 carbon atoms joined together in a ring

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Arenes




- compounds containing a benzene ring

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Naming Arenes

- short alkyl side chains, halogens and nitro groups are prefixes to 'benzene' when naming arenes

- we use 'phenyl' as a prefix to alkyl side chains greater than 7 carbon atoms long, or alkyl side chains with a functional group

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Electrophilic Substitution of Benzene

- results in a hydrogen atom being substituted by an electrophile
- is a two step mechanism:
1) the addition of the electrophile to form a positively charged intermediate
2) the loss of a H+ from the carbon atom attached to the electrophile, which reforms the delocalised ring

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Halogen Carriers

- are catalysts that make some compounds into stronger, more polarised electrophiles, in order for them to be able to attack the stable benzene ring
- accepts a lone pair of electrons from a halogen atom on an electrophile and as the lone pair of electrons is pulled away, the polarisation in the molecule increases, making the electrophile stronger
- includes aluminium halides and iron halides

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Halogenation

- benzene will react with halogens in the presence of an aluminium halide catalyst

- the catalyst polarises the halogen, allowing one of the halogen atoms to act as an electrophile

- during the reaction, a halogen atom is substituted in place of a hydrogen atom

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Friedel-Crafts Reactions

- are useful for forming C-C bonds in organic synthesis

- are carried out by refluxing benzene with a halogen carrier and either a haloalkane or an acyl chloride

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Friedel-Crafts Alkylation

- puts an alkyl group onto a benzene ring using a haloalkane and a halogen carrier

- the general reaction is:

C6H6 + R-X --> C6H5R + HX

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Friedel-Crafts Acylation

- substitutes an acyl group for a H atom on benzene
- benzene has to be refluxed with an acyl chloride
- produces phenylketones or benzaldehyde if R=H
- the general reaction is:

C6H6 + RCOCl ---> C6H5COR + HCl

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Making Nitrobenzene

- nitrobenzene is made when you warm benzene with concentrated nitric acid and concentrated sulfuric acid

- sulfuric acid is a catalyst, so it helps to make the nitronium ion, NO2 +, which is the electrophile, and is then regenerated at the end of the reaction mechanism

- the temperature needs to be kept at 50 degrees celcius