chemistry 30 – organic chemistry - part 2 to accompany inquiry into chemistry

Chemistry 30 – Organic Chemistry - Part 2

To accompany Inquiry into Chemistry

Organic Chemistry – 15.1 – Types of Organic Reactions

• A Combustion Reactions

• We will focus on complete combustions:hydrocarbon + O2(g) CO2(g) + H2O(g) + energy

• Cellular respiration is a complete combustion (but H2O(l) is produced)

• Many hydrocarbon derivatives also undergo complete combustion


• Do questions 1a, 2, and 3, page 589


• B Addition Reactions

Product has more bonds! AdditionC =

C + Y – Z - C – C

-

Y Z

seepage590-1

• Addition can occur with alkene or alkyne:

• + water (HOH) alcohol• + hydrogen (H2) alkane• + hydrogen halide (HX) alkyl

halide• + halogen (X2) alkyl

halide


• Your text has numerous examples of addition reactions on page 590 and 591

• Read about trans fats on page 592

C = C

C = C

CH2 – O – C - R

CH2 – O – C - R

CH – O – C – R

R′

R′

=

=

=

O

O

O

H H

H

H

A fat molecule:

trans linkage

cis linkage

fats are triesters!


• C Elimination Reactions

• Essentially the reverse of addition – less bonds

• Alcohols undergo elimination to produce water and an alkene

• Alkyl halides can undergo elimination to produce alkene and hydrogen halide

C = C

+ Y – Z - C – C -

Y Z

Examples on page 593


• D Substitution Reactions

• Like name implies, something leaves and is replaced by something else

• Examples pages 593 and 594

• Note that for halogens + alkanes, reaction is very slow (essentially doesn’t occur) without presence of ultraviolet light

- C – Y + A – Z - C – Z + A - Y


• Aromatics + halogens will undergo substitution, not addition


• E Esterification

• Esterification is a type of elimination reaction – water is produced

R - C – OH

=

O

+ HO - R′

R - C – O - R′

=

O

+ HOHcarboxyli

cacid

alcohol

ester

water

H2SO4

catalyst


• Example:

CH3 – CH2 – C – O - H + H - O-CH3

=

O H2SO

4


• Example:

=

O CH3 – CH2 – C – O – CH3 + HOH

CH3 – CH2 – C – O - H + H - O-CH3

=

O H2SO

4

methyl propanoate • I prefer to write it in reverse direction

(alcohol 1st) to make naming ester easier

CH3 – O – H + H – O – C – CH2 – CH3 CH3 – O – C – CH2 – CH3 + HOH

=O =O H2SO

4 methyl propanoatenow ester is written in order

of name


• Further esterfication examples on page 595 – 6

• Other examples page 596

• Do Practice Problems 1 – 3, page 596 – 7

• Do WS 15.1.5

• Do Investigation 15.A, page 597


• Summary:Reaction type

Complete Combustion

Addition Elimination Substitution Esteri-fication

Reactants Hydrocarbon* + O2

ene or yne + HOH, X2, HX, or H2

alcohol or alkyl halide

alkane or aromatic + X2

alcohol + carboxylic acid

Products CO2(g) + H2O(g) or (l)

alcohol, alkyl halide*, alkane

alkene + HOH or HX

alkyl halide ester + water

Other triple or double to single

single to double

slow; needs uv light

acid catalyst needed

Other more bonds*

fewer bonds*

Organic Chemistry – 15.2 – Polymers and the Petrochemical Industry

• Bromine test for double bonds

• Bromine, Br2, forms a brown solution (remember electrolysis of KBr(aq)

• If Br2(aq) is mixed with an alkene or alkyne, addition will occur and the brown colour will disappear in the aqueous layer

• If Br2(aq) is mixed with an alkane or aromatic, substitution (slow) will occur and the aqueous layer will remain brown…………..


• Read “Octane-Enhancing Compounds” page 599 and

• “Replacing CFC’s” page 600

• Section 15.1 – oral review – question 1 - reaction type


• Polymer: a large long chain molecule with repeating units of small molecules called monomers

• Plastics: polymers that can be heated and shaped into specific shapes and forms

• Plastics are always synthetic, though not all polymers are synthetic


• Addition polymerizationthe reaction is an addition reaction as studied earlier

• Example: polyethylene

CH2=CH2 + CH2=CH2 -CH2-CH2-CH2-CH2- + CH2=CH2

- CH2 – CH2 – CH2 – CH2 – CH2 – CH2 – and on and on


• Other addition polymers:

2 2

2

2

2 2

Cl Cl

Cl


• Condensation polymerization – water produced

• polyesters and nylons

• polyester example:

ester linkage


• nylon example:

amide linkage: same type of bond present between amino acids in proteins


• Do Practice Problems page 606, questions 7-10


• Ethene (ethylene) is required for the manufacture of many substances in Alberta’s petrochemical industry

• Ethane, obtained from petroleum refining is “cracked” to produce ethene by catalytic cracking:C2H6(g) CH2=CH2(g) + H2(g)

ethane ethene• Ethene is used to produce ethylene glycol

(ethane-1,2-diol), polyethylene, and polyvinyl chloride

Pt


• Manufacture of PVC (polyvinyl chloride):Step 1:

• Step 2:

C = C (g) + Cl2(g) - C – C - (g)

Cl Cl reaction type?

Cl Cl - C – C – (g) C = C (g) +

HCl(g)

Cl

reaction type?

HCl from step 2 reacted with more ethene to produce more Cl C

l - C – C -


• Step 3:Cl n C = C ………. - C – C – C – C – C – C -

……….

Cl

Cl

Cl

polyvinyl chloride


• Heath and Environmental Concerns:

• Vinyl chloride: was found in the 1970’s to be carcinogenic. Workers protected today by government legislation

• Manufacture and disposal of PVC may produce dioxins – highly toxicBiggest source: people burning their own garbage

Cl C = C


• Plastics do not decay or rot – problems?

• Today: recycling programs – manufacture of useful products from recycled plastics

• Note: recycling is not the cure-all. Reducing and reusing are better solutions. Why?


• Natural Polymers

• Carbohydrates: (monomer-glucose) cellulose, starch, glycogen

• Proteins: (monomer-amino acids)

• DNA


• Section 15.2 Review, page 614, question 1-6

chemistry 30 – organic chemistry - part 2 to accompany inquiry into chemistry

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