Review Sheet for Chemistry 311 Exam

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Review Sheet for Chemistry 311 Exam
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.


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