Topic 17 - Organic Chemistry (17.6 - 17.7) Flashcards

1
Q

What is organic synthesis?

A

making something new from what already exists. In organic, usually means using a familiar compound to make an unfamiliar compound. E.g. converting halogenoalkane into alcohol. Example could be..
bromoethane –> X –> ethyl propanoate
Step 1: bromoethane –> ethanol - reflux withaq potassium hydroxide
Step 2: ethanol –> ethyl propanoate - heat with propanoic acid

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2
Q
What are Grignard reactions? 
1) CO2
2) methanal
3) aldehyde
4) ketone
Formation of...
1) 3-methylbutanoic acid
2) propan-1-ol
3) pentan-2-ol
A

Heat under reflux chosen halogenoalkane with Mg in a solvent of dry ether. Haloarenes like bromobenzene used. Contain Mg covalently bonded to alkyl group and halogen

1) RMgBr –> RCOOH = carboxylic acid
2) RMgBr –> RCH2OH = primary alcohol
3) RMgBr—> RR’CHOH = secondary alcohol
4) RMgBr —> RR’R’‘COH = tertiary alcohol

Formation
1) Formation of Grignard = (CH3)2CHCH2MgBr
2) React with chosen reagent = CO2 --> 
(CH3)2CHCH2COOMgBr
3) hydrolysis using dilute acid like H2O
(CH3)2CHCH2COOH + Mg(OH)Br

Propan-1-ol
CH3CH2Br in dry ether +Mg = CH3CH2MgBr
HCHO/H2O/H+ –> CH3CH2CH2OH

Pentan-2-ol
CH3CH2CH2Br –> Mg/dry ether then CH3CHO then H2O/H+ to form CH3CH(OH)CH2CH2CH3

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3
Q

Describe technique of heating under reflux

A

Some reactionsinvolving organiccompounds slow at room temp so obvious to heat reaction mixture. Normal way to prevent volatility is heat mixture in flask fitted with reflux condenser. Vapours rising from reaction mixture during heating enter condenser and change back into liquids and return to glask so unreacted compounds react. Anti bumping granules help make boiling smooth

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