OCHEM Lab Final

solvolysis

splitting by solvent

alkene

A hydrocarbon with a double bond

dehydration (elimination) reaction

Alkenes may be prepared through a _________________________________________ of an alcohol (R-OH)

balanced equation of combustion reaction of ethane

C2H6 + O2 -----> 2CO2 + 3H2O

balanced equation of combustion reaction of propane

C3H8 + 5O2 -----> 3CO2 + 4H2O

balanced equation of combustion reaction of methane

CH4 + 2O2 -----> CO2 + 2H2O

200 mL

Calculate the quantity of 0.01 M aq NaOH needed to neutralize the HCl produced by complete solvolysis of the t-BuCl in 10 ml of 0.2 M t-BuCl in acetone

inert to chemical reactions

In the absence of a spark or a high-intensity light source, alkanes are

alkyl bromide

In the presence of light, or at high temperatures, alkanes react with bromine to form

alkyl halides

In the presence of light, or at high temperatures, alkanes react with halogens to form

(CH3)2CHCH2CH2CH2I

Which of the following compounds will undergo a SN2 reaction most readily?

because cyclohexene has a lower boiling point than cyclohexanol

Why does cyclohexene distill over to the receiving flask while cyclohexanol remains in the reaction flask?

The iodide of potassium iodide acts as a strong nucleophile and bromine and chlorine atoms are good leaving groups. Sodium iodide then increases the reaction.

Why does sodium or potassium iodide replace chlorine or bromine atoms in SN2 reactions? Explain your reasoning.

Bromide ion can not replace OH due to the fact that the bromide ion is a weaker nucleophile than OH. However, since OH is a good leaving group, it allows bromide ion to replace OH

Why does the reaction of bromide ion with 1-butanol require a strong acid to complete substitution?

because the bonds of ethane are partially broken in order to allow for bromine to fit in the molecule of ethane. bromine is added across the double bond.

Why is the reaction of ethane with bromine called an addition reaction?

alkane

a hydrocarbon with only single bonds

chemical kinetics

study of how the chemical changes in a predefined experimental condition affect the rate of a chosen reaction

3 degree (tertiary)

tert-butyl chloride has an electronegative chlorine atom attached to a __________ carbon

3, carbocation intermediate

the accepted mechanism of dehydration involves a ____ step sequence involving a _______________________

half-life (t 1/2)

the amount of time that it takes for the concentration of reactant to decrease to half of its initial concentration

positive, unsaturation

the disappearance of the bromine color is a ________________ reaction of __________________

faster

the more stable the carbocation intermediate, the _______________ the rate of dehydration will occur

linear equation

the rate law equation for a first order reaction is NOT a

k

first -order rate constant

cis isomer of an alkene

has the carbon groups attached on the same side of the double bond

trans isomer

has the groups attached on opposite side

decrease, time

the rate of this 1st order chemical reaction can be expressed as the __________________ in concentration of reactant per unit of ____________ (or the increase in the [HCl] per unit time)

E1 elimination reaction

the removal of an HX substituent results in the formation of a double bond.

H2O, CN-, HC---C-, CH3-, OH-

what are some examples of nucleophiles?

SN1 and SN2

what are the 2 different substitution reactions?

1. you can use the titration data to figure out exactly how much tBuCl we started and how much was present at each point along the reaction progress 2. you can calculate the volume of base needed is proportional to the amount of tBuCl

what are the 2 ways to get the rate constant?

1. the experimental condition 2. concentrations of reactants 3. the nature of the solvent 4. the process temperature

what can affect rates of chemical reaction?

the cyclohexanol molecule will lose a molecule water as the reaction proceeds. Cyclohexanol will lose the -OH group and a -H atom on the adjacent carbon to form a carbon-carbon double bond

what happened in the dehydration reaction in the experiment?

because the base deprotonates one of the phenolic OH groups

what is the reason for bromthymol blue indicator exhibiting blue?

phosphoric acid allows cyclohexanol to be protonated and which generates a stable OH2 leaving group and a carbocation. It also completes the elimination by forming the C-C double bond by removing the hydrogen of cyclohexanol.

what role does phosphoric acid play in this reaction?

7.4 ml of cyclohexanol and 1.75 mL of 85% H3PO4

what was added to the rbf of experiment 9?

combustion

when a hydrocarbon burns in presence of oxygen

purple ------> brown

when potassium permanganate reacts with an alkene what color change occurs?

t-butyl alcohol

which of the alcohols named below will react fastest with HCl to form the corresponding alkyl chloride via an SN1 pathway?

by heating the alcohol in the presence of an acid catalyst, such as phosphoric acid (H3PO4)

how is a dehydration reaction of an alkene achieved?

aromatics

hydrocarbon with a benzene ring

window light

if the bromine test is negative, shine __________________ directly on tube for 4-5 minutes

17.1 g

Please determine the correct mass in grams if you were to start with 0.15 moles of 2-methylcyclohexanol

carbocation

SN1 reactions produce a racemic mixture because the mechanism involves a intermediate

inversion of configuration

SN2 reactions involving a chiral halide/substrate usually proceed with:

proceed with nucleophilic backside attack and are stereospecific

SN2 reactions usually

As temperature increases, the molecules start to collide more frequently allowing it to overcome the activation energy. (It lowers the activation energy)

The measurement of reaction rates as a function of temperature provides information on the activation energy for the reaction. Please explain

true

The rate of a first order chemical reaction is proportional to the concentration of electrophile.

reactive

Unsaturated hydrocarbons such as alkenes and alkynes are much more ________________ than the parent alkanes

primary halide and strong Nuc-

What are the experimental factors that favor a SN2 reaction?

dark red -----> colorless (bromine and alkene) purple -----> brown (potassium permanganate and alkene)

What changes in color occur when bromine or KMnO4 reacts with an alkene?

substitution, nucleophilic, unimolecular

What does the term SN1 mean?

the product of combustion of an organic compound is carbon dioxide and 2 molecules of water. This occurs when methane gas reacts with 2 molecules of oxygen

What is the product of combustion of an organic compound? Give an example

products

What side would the equilibrium favor if we diluted (added water) to the phosphoric acid (H3PO4) before starting the reaction?

The effect of carrying out reaction 1 with concentrated iodide solution would be that it would give it a SN2 reaction.

What would be the effect of carrying out Reaction 1 with concentrated sodium iodide solution?

87%

What would the actual percent yield of the above reaction be if we started with 5.4 g of 2-methylcyclohexanol and isolated 3.9 g of 1-methylcyclohexene?

8.4 g

What would the theoretical yield (in grams) for the given reaction if you started with 10.0 g of 2-methylcyclohexanol?

addition reaction, disappears quickly

When bromine (Br2) reacts with alkene, it undergoes ________________________________ and the dark red color of Br2 _____________________________

Nucelophilic substitution

a reaction in which an incoming nucleophile replaces an existing functional group

SN1

a two step reaction, involving the formation of a carbocation intermediate, followed by a nuceophilic attack

cyclohexane was present due to the fact that the color change went from red to colorless

after dehydration reaction and transferring 10 drops of it into test tube A with 1 drop of 2% Br2, what was present and why?

carbocation, E1 elimination reaction

because the carbocation is a high-energy intermediate, the rate of dehydration depends upon the structure of the _____________________________, and therefore, is considered an _________________________________________

high temperatures

bromthymol blue indicator does NOT work properly under

positive

brown manganese dioxide (MnO2) precipitate in a potassium permanganate test indicates a __________________ reaction

larger

carbocations are more stable (lower in energy) when they have a ___________________ number of alkyl groups adjacent to them

CH3-HC--CH-CH3

condensed structure of cis-2-Butene

(CH2)4CH--CH

condensed structure of cyclohexene

CH2CH2

condensed structure of ethene

CH2CHCH3

condensed structure of propene

yellow

in acidic conditions, bromthymol blue indicator exhibits

blue

in basic conditions, bromthymol blue indicator exhibits

SN2

involves 2 different reactants and one reaction rate that determines the steps. Is a one-step reaction involving a back-side nucleophilic attack

activation energy

measurements of reaction rates as a function of temperature provides information on the ______________________________________ for the reaction

lone pairs of electrons and may carry a negative charge

nucleophiles have

positive charged centers (i.e carbocation)

nucleophiles seek

alkenes

potassium permanganate can ONLY react with

alkenes, alkanes, aromatics

potassium permanganate reacts with _______________, but not ______________ and _________________________ compounds

monitor the validity of a proposed mechanism

reaction kinetics can be used to

the decrease in concentration of reactant(s)/the increase in concentration of product(s) as a function of time

reaction rates can be determined by monitoring