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WACE Chemistry > Ch. 9 Synthesis Reaction > Flashcards

Ch. 9 Synthesis Reaction Flashcards

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1
Q

what is synthesising

A

> 

to produce a specific product
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2
Q

what is the reaction pathway

A

the sequence of chemical reactions for an overall chemical change (reaction mechanism)

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3
Q

what are intermediates

A

a product of one reaction that is used as a reactant in the next reaction of a reaction pathway

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4
Q

what is retrosynthetic reaction

A

for determining the reaction pathway for a synthesis reaction that involves starting with the product and working backwards by identifying simpler substances

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5
Q

explain synthesis of ethanal

A

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

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6
Q

what four factors are considered when deciding appropriate steps for chemical reactions

A

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

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7
Q

what is the contact process an example of

A

multistep process and linear

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8
Q

what is the contact process

A

series of reactions to produce sulphuric acid

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9
Q

explain the three steps of the contact process

A

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

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10
Q

what are the intermediates in the contact process

A

sulfur dioxide and trioxide

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11
Q

what are the two types of pathway sequences

A

linear and convergent

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12
Q

explain the linear sequence

A

reaction steps follow one after the other in a linear progression

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13
Q

explain convergent sequence

A
  • Uses different reaction pathways and then the products from these are combined as reactants in another reaction
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14
Q

what is an example of convergent sequence

A

esterification

  1. Production of the appropriate carboxylic acid
  2. Production of the appropriate alcohol
  3. Reacting carboxylic acid with alcohol
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15
Q

what conditions help maximise yeild

A
  • removal of product
  • recycling reactants
  • temp
  • pressure
  • catalyst
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16
Q

how does removal of product effect yeild

A

decrease concentration of product= favor forward reaction (Equilibrium shifts to right)

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17
Q

how does recycling reactant effect yeild

A

recycling unused reactants= less wastage. Increases concentration of reactant // favor forward (Equ. shifts to right)

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18
Q

how does temp effect yeild

A

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

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19
Q

how does pressure effect yeild

A

pressure of gaseous system affect position of equ,// pressure used should favour reaction so equ. goes right, cost and safety considered

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20
Q

how does catalyst effect yeild

A

increase rate of production of product. while doesn’t increase yield, product produced in shorter time

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21
Q

how does temperature effect the contact process

A
  • 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
22
Q

how does pressure effect the contact process

A
  • 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
23
Q

what is the hater process

A

used in production of ammonia from nitrogen and hydrogen gas

24
Q

how does temp effect haber process

A
  • 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
25
Q

how does pressure effect haber process

A
  • Increase pressure= increase rate of reaction as increases concentration of reactants // increase number of collisions
  • Yield also increased by pressure
    o high pressure favors reaction that produces less amount of gaseous molecules (in Haber= award reaction + // yield is increased)
  • Although higher pressure increases yield and rate, extreme pressures= risk and cost
    o Expensive to produce and maintain high pressure
    o Risk of exposition if pressure greater than container can withstand
  • // pressure of 200 atm provides balance b/w high rate and yield and cost associated with even higher pressures
26
Q

how are enzymes catalysts

A

o Proteins with properties (shape) allow to them to interact with reactants of a reaction

27
Q

define theoretical yield

A

amount of product that can be theoretically be produced from the reactants

28
Q

formula for percentage yield

A

actual mass/theroetical mass x 100

29
Q

what is the process for percentage yield

A
  1. theoretical yield (mole ratio)

2. formula

30
Q

what is the structure of soaps

A
  • Consist of long hydrocarbon chain, or tail, with a carboxylate ion (-COO-) at one end (the head)
  • A positively charged sodium or potassium ion is bonded to carboxylate ion, making soap molecule a sodium (or potassium salt)
31
Q

how are soaps made

A

hydrolysis of fats in a saponification reaction

32
Q

what does tryglyceride react with in order to saponifacte

A

sodium hydroxide

33
Q

what happens in the saponification reaction

A
  • When triglyceride reacts with sodium (or potassium) hydroxide, the ester bond break and an alcohol and three alkyl carboxylates are formed
34
Q

what about th structure of soaps enable them to clean

A
  • Able to clean because they can bond with both polar and non-polar substances
    o The hydrocarbon chain= non-polar (hydrophobic)
    ♣ Can bond to non-polar dirt and grease
    o Head= polar (hydrophilic)
    ♣ Due to presence of carboxylate ion
    ♣ Can form bonds with water
35
Q

what are the steps in soaps working

A
  1. Soap molecules surround dirt or grease on a surface, with their hydrophobic tails embedded in dirt or grease, leaving hydrophilic ends on outside to bond with water molecules
  2. When water is agitated, water molecules pull up soap molecules, which pull on dirt= lifts dirt away from surface and more soap molecules able to surround it
  3. When soapy water is washed away, the dirt is taken with it
36
Q

what is the problem with soaps and why are detergents better

A
  • Problem with soaps= they don’t lather up in water containing calcium or magnesium ions (hard water)
    o When calcium or magnesium ions combine with carboxylate ions on soap= insoluble product (=scum)
  • Detergents do not contain the carboxylate ion and // do not precipitate
37
Q

what is different about the structure of detergents as opposed to soaps

A
  • the hydrocarbon tail in detergents is an alkylbenzene while the polar head is sulfonate (SO3-) ion
38
Q

what is atom economy formula

A

mass of atoms product/ mass of atoms in reactants/ 100

39
Q

what is an alpha amino acid

A

Amino acids containing an amino group bonded directly to the alpha carbon (carbon #2 as next to carboxyl)

40
Q

what is a main characteristic of alpha amino acids

A
  • formation of zwitterions
41
Q

what is a reaction of alpha amino acids

A

condensation to form polypeptides (proteins) (forms amide bonds)

42
Q

define primary structure of amino acids

A

sequence of amino acids in a protein

43
Q

explain secondary strycytes of a protein

A

(a- helix and b pleated sheets) result from hydrogen bonding of amides and carbonyl (helix= bonds within chain, sheet= bonds between adjacent)

44
Q

explain terry structures of proteins

A
  • overall three dimensional shape

- due to interaction b/w side chains a amino acid

45
Q

what are bonds of tertiary structures

A
  • disuflide, hydrogen, dipole dipole. dispersion, ionic
46
Q

biodiesel is synthesised using what two types of catalyst

A
  • base

- lipase

47
Q

explain base catalyst of biodiesel

A
  • Common= base catalysts (sodium/potassium hydroxide)
    o Most economical
    o 98% yield
    o Requires low temperatures
    o Produces high temps= risks
    o Forms soap, which reduces yield of ester
    o Expensive to purify glycerol due to presence of base
48
Q

explain lipase catalyst of biodiesel

A
  • Enzyme= biological catalyst
    o Lipase catalyst breaks down fats and // increase rate of reaction
    o Overcomes problem of soap production and // enables higher yield of biodiesel
    o Expensive
49
Q

what are two examples of plastics

A

polythene, polytetraflouroethene

50
Q

what are two explampels of condensation polymers

A
  • nylon

- polyethylene terephthalate (PET)

51
Q

difference between hydrolysis of ethene and fermentation to produce ethanol

A

fermentation better (although impure and slow, uses raw materials, lower temp and pressure, and little energy required)

WACE Chemistry (8 decks)

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