ORGANIC CHEMISTRY
AS CHEM. STUDY GUIDE
DEFINE FREE RADICALS
• Atoms (or groups of atoms) with unpaired electrons
DEFINE HOMOLYTIC FISSION AND DESCRIBE HOW ITS
PRODUCTS ARE WRITTEN IN AN EQUATION
• When a covalent bond is broken to produce two free radicals
• Energy provided by UV light
• Unpaired electrons are represented by a dot
DESCRIBE HETEROLYTIC FISSION
• The more electronegative element in a bond takes both electrons
• Movement showed by a curly arrow
• **carbocations are positively charged ions with carbon**
ISOMERISM
Structural Isomerism:
chemicals with same formula
behave differently because of
different structures
Chain:
Different due to
branching (moving
carbon)- mostly
changes boiling point
Positional:
Changes
position of
functional
group
Stereoisomerism:
Same atoms joined to each other
in different spatial arrangements
Geometric
(cis-trans) –
double
bonds only!
Optical isomers
(enantiomers):
4 different ends =
chiral; mirror image
– can’t be
superimposed
DESCRIBE PHYSICAL PROPERTIES OF ALKANES. INCLUDE:
GENERAL FORMULA, POLARITY, TYPE OF BONDS AND
ANGLES, AND VOLATILITY PATTERNS
• CnH2n+2
• Nonpolar due to weak van der Waals forces
• Not very inert which is why it is not readily attacked in reactions. Other nonpolar
reagents can react with alkanes, mostly halogens, in the presence of UV light
• Sigma bonds – 109.5 degrees
• Volatility decreases as carbons increase (b.p. increases)
• More electrons means more energy needed to break bonds
• More branches lower m.p./b.p. because the straight chains can pack more tightly
together whereas branches start to form a circular shape which leaves gaps
DESCRIBE PHYSICAL PROPERTIES OF ALKENES. INCLUDE:
GENERAL FORMULA, TYPE OF BONDS, AND SATURATION
• CnH2n
• Pi and sigma bonds (overlap of p orbitals)
• Unsaturated (presence of pi bond)
• Indicates it will undergo addition reactions with hydrogen and other
chemicals to break double bond
• Oils (like vegetable oil) are made of double bonds while hard butters, etc.
are saturated single bonds
WRITE THE EQUATION FOR COMPLETE AND
INCOMPLETE COMBUSTION OF BUTANE
1
• C4H10 (g) + 6 2O2 (g)
1
• C4H10 (g) + 4 2 O2 (g)
4CO2 (g) + 5H2O(l)
4CO(g) + 5H2O(l)
WRITE THE ENTIRE MECHANISM THE SUBSTITUTION
REACTION OF METHANE AND CHLORINE (FREE RADICAL
SUBSTITUTION) AND REACTION EQUATION
Reaction: CH4(g) + Cl2(g)  CH3Cl(g) + HCl (g)
1. Initiation: homolytic fission of chlorine (in the presence of UV light)
• Cl—Cl (g)  Cl. (g) + Cl. (g)
2. Propagation: a chain reaction that will continue until termination step
• Cl. + H—CH3 (g)  Cl—H(g) + CH3.(g)
• CH3. (g) + Cl—CL (g)  CH3Cl(g) + Cl. (g)
3. Termination: removes free radicals by bonding
•
Cl. + Cl.  Cl2
• CH3. + Cl.  CH3Cl
• CH3. + CH.  CH3CH3
WHAT TYPE OF REACTIONS DO ALKENES UNDERGO?
LIST THE THREE TYPES OF THEM AND THE CONDITIONS
NEEDED FOR THE REACTION
• Electrophilic addition
• Hydrogenation (addition of hydrogen to make alkane)
•
H(g) + alkene(g)  saturated alkane
•
Nickel catalyst, 450 K, 1000 kPa
• Halogenation (addition of a halogen)
•
Will add Br, Cl, or I to each carbon at end of double bond
•
Test for an alkene is to shake alkene with bromine water b/c it is orange but the alkene will turn it colorless
•
CH3CH=CH2 + Br2  CH3CHBrCH2Br
• Hydration (addition of water)
•
Makes alcohol
•
600K, 6MPa, solid catalyst of H3PO4
• Addition of hydrogen halide
•
Done through acid solution (like hydrochloric acid) and halogen goes on carbon with least amount of hydrogens
•
Reactivity increases from HF to HI (HF only reacts under pressure)
DESCRIBE MECHANISM OF ADDITION WITH ALKENES
(BROMINATION)
• Double bond polarizes bromine
• Pi bond breaks and forms covalent bond with a bromine
• Bromine undergoes heterolytic fission (takes both electrons) while the molecule becomes a carbocation
• Bromide ion and carbocation rapidly form
• Bromine is the electrophile
DESCRIBE THE CONDITIONS AND REACTIONS OF
ALEKNES WITH POTASSIUM MANGANATE(VII)
Cold and dilute
• React readily at room temp
• Shaken with dilute acidified or alkaline solution
• Purple color disappears and diol forms
• CH2=CH2 + H2O + [O]  HOCH2CH2OH
ethane-1,2-diol
Heated
• Break double bond and add double bonded
oxygen to each side
• Aldehyde further oxidizes to carboxylic acid
(make the hydrogen an –OH )
• Ethene  aldehyde  methanoic acid  CO2
and H2O
• Ketones stay ketones (no hydrogens attached)
SHOW ADDITION POLYMERIZATION REACTION OF
EHTENE AND DEFINE REPEAT UNIT AND MONOMER
• Repeat unit: section of the polymer that is
repeated to produce polymer
• Monomer: alkene from which polymer is
made
• Name by saying poly(chloroethene) or
whatever should go inside parenthesis