Review Sheet for Chemistry 311 Exam
Study all prelab, postlab and introduction questions.
Besides topics covered in prelab, postlab and introduction questions
Mechanisms
SN1 and SN2 (specific to the reactions carried out and the formation of the
precipitate)
Esterification
Dibenzalacetone synthesis
Reduction
Benzoin condensation (specifically the roles thiamine plays), where water and OH-
came from in the mechanism
Calculations
Theoretical and % yield
Percent recovery for recrystallization
Partition Coefficient for Extraction – single and multiple extractions
Raoult's Law for Distillation
Balanced equations of:
Reactions that occured in acid-base extraction
all synthesis (major products)
all side products from synthesis
all intermediates in the synthesis
all reactions (stepwise) that occur during the synthesis (This are for experiments
where the reaction happens in two or more steps – indicated by addition of a
reactant or observation)
Structures and names of all starting materials, products and side-products for all
synthesis
Safety rules and regulations
- clothing and safety attire, eye protection, contact lenses, do’s and don’ts
- treatments for chemical on parts of the body, the eye (including do’s and don’ts)
- treatments for burning clothing (including do’s and don’ts)
- remedy for burning reagents (including do’s and don’ts)
Modifications provided in "hints for preparation" to help reactions proceed smoother.
All sketches of apparatus (label with appropriate names from pg 10). Be able to draw
the apparatus.
Functions of parts of the apparatus.
Placement of all parts of apparatus with relation to other parts– why should certain
parts be placed in a certain manner.
You should be able to tell if an apparatus is set up correctly or not.
Melting Points
Why are melting points carried out?
Definition of the melting point of a pure compound.
What is the criteria for impurity?
What forces affect melting point? (Also, consider the effect on the melting point of
larger molecules, symmetrical molecules and R,S isomers, and hydrogen bonding
molecules)
Define eutectic point (two ways mentioned in notes) and eutectic temperature
Melting point composition graph
Mixed melting points experiment
How sample is prepared? Why sample should be prepared in a specific manner?
Criteria for sample before packing and how it should be packed.
How should sample be heated and why? What may happen if you heat the sample
too quickly?
Definition of melting range
Why does sample shrink before melting
What happens if you have too much sample
What happens if sample is coarse (not powdered)
Recrystallization
Reason for carrying out
Picking solvent: like dissolves like
Requirements for solvents with respect to solute and impurities
Requirement for solvents for solvent pairs
Why solvent pairs are used
How to minimize loss of product in crystallization, collecting and washing steps – why
does product get lost in these steps
Requirements when cooling
Remedies for unsaturated solution, supersaturation
Definition of superheating and prevention – how boiling sticks and stones achieve
their purpose.
Why crystals oil out – remedies and prevention
Small powdery crystals – why they form and how to prevent, why large crystals are
preferred
Activated charcoal – purpose and how it works
Why is it important that boiling stick is removed during cooling process?
Extraction
Reason for carrying out
Flowchart on how to separate strong acids, weak acids, bases and neutral
compounds
Why extractions are carried out in the sequence they are (weak base then strong
base)
Reactions of the acid-base extractions
Requirements for extraction solvents
Emulsions – definition, causes, and remedies
How to decrease solubility of organic substance in aqueous layer
Why drying agent was used? What observations indicate that an organic layer is dry?
You must know what substance(s) you have used as a drying agent in the
experiments you have carried out.
Criteria for choosing drying agent
How do you ensure all product is transferred from drying agent
Advantages of t-butylmethyl ether and disadvantages of diethyl ether
Why don’t you get 100% recovery?
TLC
Precautions to take when spotting, developing and visualizing
Why should bores of capillaries be small
Characteristics of solvents that allow them to migrate rapidly
Adsorbent materials and specific uses (what kind of adsorbents would be better for
what kind of substances)
Table 9.2 (Order of solute migration)
Uses of TLC and how it is used– all 6
Effects of using too polar or too nonpolar a solvent
Distillation
Reason for carrying out
Insulation of apparatus
Wrapping with a wet paper towel – why?
Position of the thermometer
Position of end of sidearm
Boiling point composition graph – Fig. 5.2 and 5.4 – phases in the graph and how to
interpret data from the graph (liquid and vapor composition of mixture)
Uses of simple and fractional distillation – what kinds of mixtures are suitable for
each kind of distillation
Behavior of temperature during a simple or fractional distillation of a mixture.
Definition of azeotrope (minimum and maximum) – recognize azeotrope on boiling
point composition graph
Boiling points of miscible and immiscible mixtures with relation to pure compounds
Definition of hold up
Use of a packing material and criteria for choosing
Steam distillation – uses, what kind of mixture used in steam distillation - difference
between vacuum distillation and steam distillation
What requirement is necessary for boiling point in steam distillation to be constant?
Precautions about distilling to dryness, distilling in closed system.
Sources of error in a distillation
Nucleophilic Substitution
Factors that affect SN1 and SN2 (general and specific to experiments carried out)
-structure of alkyl halides, temperatures, solvents, leaving groups, etc. (also know
why trends are the way they are)
- relative rates of reactions and the reason for those relative rates.
- the importance of using the exact same amount of alkyl halide and nucleophile in
each test tube
- possibility of a false positive in a reaction
- why vinyl and aryl halides don’t undergo SN1 or SN2
- products when starting alkyl halide is chiral and why.
- why do the Br- and Cl- not attack the alkyl iodides that form in the SN2 reaction
carried out?
Esterification
How Le Chatelier principle could be used in this reaction (both methods)
- why was one used and not the other?
How water could be removed? (both methods)
-why was one used and not the other?
Why was apparatus set up the way it was? (on an angle, wrapping the condensor
with wet paper towel etc)
Role of each step of the reaction (including the simple distillation that was asked for
in the procedure but not carried out)
Purpose of IR and interpretation of IR spectrum
Role of resin and advantages
Disadvantages of using traditional acid catalyst and purpose for each of the steps
needed to be carried out if traditional acid catalyst is used
Catalytic acid
Sources of error
Reasons reaction may not go to completion
Reduction
How reduction is characterized in organic chemistry
Why NaBH4 used instead of LiAlH4
Why was ethanol used as solvent instead of ether
Why was excess NaBH4 used in the reaction
Specific side products and why they form
Role of each addition of water
Role of ice bath
Why recrystallization carried out
Sources of error
Dibenzalacetone synthesis
Specific side products and why they form
Mixed aldol – drawback and how to minimize mixture of products
Role of sodium hydroxide
Role of water and its source
Reason for washing crystals with water, what may happen if you don’t
Why recrystallization carried out
Where each species that carries out a specific step in the mechanism originates
Ease of water leaving – why
Requirements for starting materials for aldol addition and condensation
Formation of enolate (why it occurs)
Catalytic base
Sources of error
Benzoin condensation
Advantage and disadvantage of thiamine catalyst
differences between benzoin and aldol condensation – product and starting material
Why two moles of hydroxide ion necessary
Why TLC used
Why recrystallization might have been carried out
Sources of error.