Ch. 9 Synthesis Reaction Flashcards
(51 cards)
what is synthesising
>
to produce a specific product
what is the reaction pathway
the sequence of chemical reactions for an overall chemical change (reaction mechanism)
what are intermediates
a product of one reaction that is used as a reactant in the next reaction of a reaction pathway
what is retrosynthetic reaction
for determining the reaction pathway for a synthesis reaction that involves starting with the product and working backwards by identifying simpler substances
explain synthesis of ethanal
ethanal (aldehyde w/ 2 carbons) can be made from ethanol (primary alcohol w/ 2 carbons). Ethanol can be made form ethene, // initial reactant would be ethene
what four factors are considered when deciding appropriate steps for chemical reactions
o Other possible products, side reactions= unwanted products
o Availability and cost for reactants
o Conditions for reaction e.g. temperature and pressure
o Other chemicals required e.g. catalysts
what is the contact process an example of
multistep process and linear
what is the contact process
series of reactions to produce sulphuric acid
explain the three steps of the contact process
Step 1. Production of sulfur dioxide through combustion of sulfur, or sulfide ores
Step 2.Sufulr dioxide reacts with oxygen to produce sulfur trioxide
Step 3. Sulfur trixode then dissolved in concetrated sulfruci acid before reacting with water to produce sulfuric acid
what are the intermediates in the contact process
sulfur dioxide and trioxide
what are the two types of pathway sequences
linear and convergent
explain the linear sequence
reaction steps follow one after the other in a linear progression
explain convergent sequence
- Uses different reaction pathways and then the products from these are combined as reactants in another reaction
what is an example of convergent sequence
esterification
- Production of the appropriate carboxylic acid
- Production of the appropriate alcohol
- Reacting carboxylic acid with alcohol
what conditions help maximise yeild
- removal of product
- recycling reactants
- temp
- pressure
- catalyst
how does removal of product effect yeild
decrease concentration of product= favor forward reaction (Equilibrium shifts to right)
how does recycling reactant effect yeild
recycling unused reactants= less wastage. Increases concentration of reactant // favor forward (Equ. shifts to right)
how does temp effect yeild
Temp= should favor forward reaction so Equ. lies as far to right as possible) + at same time, effect on rate of reaction and cost of heating considered
how does pressure effect yeild
pressure of gaseous system affect position of equ,// pressure used should favour reaction so equ. goes right, cost and safety considered
how does catalyst effect yeild
increase rate of production of product. while doesn’t increase yield, product produced in shorter time
how does temperature effect the contact process
- Combustion of sulfur dioxide in 2nd step= exothermic (-196kJmol-1) (release heat)
o increase in temp= increase in percentage of particles with enough energy for successful collision > increase rate of reaction - However increase in temp favours endothermic which favours endothermic (reverse reaction)
o lead to decrease yield of sulfur trioxide
o // compromise of 400-450 degrees used - allows relatively high yield of sulfur trioxide
how does pressure effect the contact process
- Pressure for second reaction= 1-2atm
- High pressure would increase rate of reaction + yield of sulfur trioxide
o rate increase: as increase concentration of reactants // increased collision
o increasing yield: as more gaseous molecules in reactants than products > increase pressure // favour forward reaction // equ. shift to right - However, expensive to produce + maintain high pressure safety; cost outweighs benefits gained // lower pressure used
what is the hater process
used in production of ammonia from nitrogen and hydrogen gas
how does temp effect haber process
- Increase temp= increase rate of reaction as more particles have sufficient energy for successful collision
- Decreasing temp will increase yield as favors exothermic reaction (forward reaction in Haber process)
- // decreasing temp= increase yield of ammonia
- Cost considered= expensive to heat chemicals to extreme temps // befits offset cost
- // compromise made b/w rate, yield, cost
