question

The melting point range would not be affected

answer

How would the melting range of a pure organic material be changed if there was a tiny shard of broken glass inside the melting point capillary?

question

a eutetic is a mixture of two components that generate the lowest possible melting point

answer

What is a eutetic?

question

Because it is possible that one particular combination of materials generates a eutectic.

answer

Why is it good practice to perform a mixed melting point determination at two different ratios of unknown to known materials in the melting point capillary?

question

The upper limit of the melting temperature range occurs when the last remaining crystal melts. he lower limit of the melting temperature range occurs when the first crystal starts to melt. Pure substances typically have a melting range of less than 2 degrees Celsius.

answer

What statements about melting point determination are true?

question

The melting temperature range of an impure sample is lower than that of a pure sample. The melting temperature range of an impure sample is broader than that of a pure sample.

answer

When comparing melting temperature ranges of pure and impure samples, which of the following statements describes the melting temperature range of an impure sample?

question

Rf is a number that describes the position on a spot on a chromatography plate relative to the position of the solvent on the chromatography plate maximum value is 1. minimum value is 0.

answer

What is retention factor? what is the maximum retention factor? minimum?

question

extraction, chromatography, distillation

answer

what are the four major methods of purification used in the chemistry lab?

question

when the organic material is a liquid

answer

whan is recrystillization not a suitable method to purify an organic material?

question

least

answer

the least polar substance will be the ___ (most/least) soluble in water.

question

% recovery= (mass after recrystillization/initial mass)*100

answer

How do you calculate % recovery?

question

the solvent should react with target substance, should dissolve a moderate amount of the target substance near boiling point but only a small quantity near 0. Should be easily able to remove the solvent from purified product.

answer

what are features of a good solvent for recrystillization?

question

whenever the methyl groups and every other large group is 180 degrees away from each other

answer

when are newman projections a representation of a global minimum?

question

steric strain will decrease

answer

Gauche comformation of butane occurs whenever their is a 60 degree angle between c1-C2 bond and C3-C4. There is steric strain present. Would it decrease/increase if the dihedral angle was increased?

question

E(strain)=stretch+angle+torsion+steric

answer

What is the energy equation relating strain?

question

torsional strain increases

answer

Knowing that E(strain)=stretch+angle+torsion+steric. Would torsion decrease or increase when the dihedral angle of gauche butane is increased from 60 to 65?

question

...

answer

what are diaxial interactions?

question

Attenuated Total Refelctance

answer

IR is recorded using an ATR. What does ATR stand for?

question

Same ATR sample holder can be used for liquids and solids and ATR crystal cannot be degraded by water

answer

In which ways is the use of an infrared spectrophotometer fitted with an ATR sample advantageous over a beam-through-sample spectrophotometer?

question

1400-400Cm-1

answer

What region of an infrared spectrum is most useful for distinguishing between isomers that contain the same functional group?

question

4000-3000

answer

where can you find O-H for carboxylic acids on an IR?

question

1800-1640

answer

where can you find C=O ester on an IR?

question

1600 cm-1

answer

where can you find C=C alkene on an IR?

question

a non-destructive way to detect impurities within a sample and detect and identify functional groups of a sample

answer

what can we use IR for?

question

highest:pentanal benzaldehyde lowest:cinnamaldehyde

answer

How do benzaldehyde (phenyl witha n aldehyde), pentanal, cinnamaldehyde(aldehyde, double bond,phenyl) rank in terms of their C=O stretching frequency?

question

ratio of a substances mass to its volume measure in g/ml

answer

what is density?

question

Dissolve the mixture in dichloromethane, shake with sodium hydroxide, collect the aqueous layer, and reacidify to force precipitation of the eugenol.

answer

Eugenol, the essential oil found in cloves, is insoluble in water. The alcohol group in eugenol is dramatically more acidic than regular straight-chain alcohols. How could eugenol be separated from a mixture of other non-acidic molecules?

question

If its miscible with water

answer

what makes a solvent unsuitable for solvent extraction in an aqueous solution?

question

you add acid to the three componenet mixture

answer

what do you add to convert the benzocaine into a water-soluble salt?

question

he recorded boiling point will be lower than actual because the bulb is not exposed to the hot vapor.

answer

What error is introduced if the bulb of the thermometer, or the thermocouple, is too high in the distillation apparatus?

question

amount of sample detected is proportional to the peak area and stationary phase is a very high-boiling liquid absorbed onto fire brick

answer

What are some facts about G.C. trace?

question

water contains dissolved salts that can degrade the column, water signals are very broad and make interpretation of other peaks difficult

answer

Describe why moisture must be excluded from any sample injected into the G.C.?

question

if there is a hole in the septum and needle may be partially blocked

answer

which of the following experimental errors would lead to the observation of small peaks in the G.C. trace?

question

sample is too concentrated and column is overloaded

answer

name two errors that can ocurr that leads to the peaks trailing off during the G.C. trace?

question

four times

answer

For a packed column, doubling the length essentially doubles the number of theoretical plates. This will increase the effectiveness of the separation by the square root of 2. In order to double the separation, one would need to increase the column length _______.

question

The use of a polar GC column will separate the liquids based on differences in polar interactions and volatility.

answer

how is it possible to separate two liquids with exactly same boiling point by gas chromatography (G.C.) when it cannot be done by fractional distillation?

question

less than 1 ml of the sample is available components of the mixture arent thermally stable components of the liquid mixture have identical boiling points only a small amount of pure sample is needed

answer

what are characteristic situations when prep G.C. should be used?

question

whenever several liters of sample need to be seperated

answer

what is characteristic of a situation in which we use frational distillation?

question

pros: *cheaper than helium *can be generated at the GC instead of from gas tanks *greater difference between carrier gas and sample than nitrogen Cons: *explosion hazard

answer

The carrier gas in a G.C. separation is usually an inert gas such as nitrogen, helium, or argon, but can also be hydrogen. What are the pros and cons of using hydrogen as a carrier gas in a G.C. separation?

question

one or more components is thermally unstable and one or more components is not volatile

answer

what physical properties prevent a sample mixture from being analyzed by GC?

question

a heated injector creates flash vaporization which allows separation at temperatures lower than the boiling point of the sample the wire in the thermal counductivity detector needs to be cooled by the eluent in order to register a signal

answer

during G.C. the injection port and detector are heated to a higher temperature than the column.. why?

question

retention time decreases

answer

what happens to retention time if the column temp is increased?

question

retention time increases

answer

what happens to retention time if the carrier gas flow is decreased?

question

retention time increases

answer

what happens to retention time if the amount of sample injected is doubled?

question

because this avoids loss of sample

answer

why is the detector fitted to the prep G.C. a TCD and not a FID?

question

we dont rinse the syringe with acetone we rinse it with sample instead

answer

what do we do to avoid the introduction of a spurious peak into the G.C. trace?

question

to preserve the purity of the sample because there is a lag between being detected and eluted

answer

why do we wait for the second peak to be on the rose before beginning its collection?

question

F T T T F

answer

T/F silica is toxic. hexane is flammable ethyl acetate is flammable. acetone is flammable. it is acceptable to handle TLC plates with bare hands.

question

to create an atmosphere saturated with developing solvent which stops the vapors from evaporating as it rises up the plate

answer

why is there usually a piece of filter paper in the TLC developing chamber?

question

to get as small of a dot but a concentrated dot

answer

what are the two reasons why we spot multiple times?

question

True

answer

T/F If compound A has a smaller Rf value than compound B, we can conclude that compound A is more polar than B.

question

true

answer

T/F? Less polar compounds travel faster on a TLC plate than more polar compounds.

question

Eugenol acetyl coenzyme A precursor acetogin limonene isopentyl diphosphate precursor terpene

answer

Catagorize into two: Eugenol limonene acetyl coenzyme A precursor acetogin limonene isopentyl diphosphate precursor terpene alkaloid steroid

question

(P_A/P_B)=(n_A/n_B) X_a=(n_a/(n_a+n_B))

answer

How do you calculate mole fractions?

question

m%A= (X_a*mm_a)/ ((X_a*mm_a)+(X_B+mm_B))

answer

How do ou calculate mass %?

question

ethyl acetate on top water on top

answer

what will be in the top? ethyl acetate vs.water water vs dichloromethane?

question

you figure out which one is the limiting reagent you convert the LR to moles you do a mole to mole ratio you multiply it by the mm of the other

answer

How do you calculate theoretical yield?

question

actual/theoretical *100

answer

How do calculate percent yield?

question

nucleophile attacks the backside of the carbon and bumps off the LG 1-bromobutane when heated with 2-naphthol in the presence of NaOH

answer

How do SN2 reactions occur?

question

false

answer

T/F Lachrymators like allyl bromide are specifically dangerous because they are an explosion hazard

question

true

answer

Sodium Hydroxide can cause severe damage to skin and eyes and gloves or goggles are necessary

question

fastest:water formic acid methanol ethanol acetone acetic acid

answer

For sn1 solvolysis of t-butyl chloride, rank the solvents from the fastest reaction to slowest reaction

question

first the leaving group leaves the nucleophile attacks the carbocation intermediate it gets deprotonated forms alcohol

answer

How do Sn1 conditions occur?

question

to make polar impurities less soluble in the organic layer

answer

why was the organic layer shaken with saturated chloride solution in the prep of alkyl halides?

question

to test for free Cl- ions an indication of a tertiary/benzylic carbpcation

answer

why were a few drops of silver nitrate solution added to the organic product?

question

shook the organic layer with sodium bicarbonate solution

answer

To gently neutralize the acidic reaction.. we ________ (prep of alkyl halides)

question

to exclude water from the product and push the equilibrium to the right

answer

Why did we perform the reaction in HCl in which the organic halide was not soluble?

question

R-F Slowest R-Cl R-Br R-I Fastest

answer

In regard to the E2 mechanism, rank the leaving groups in order of increasing reaction rate. I,F,Br,Cl

question

sodium dichromate and chromic acid

answer

What are common oxidizing agents?

question

safe, inexpensive, and environmetallly sound

answer

compared to the dichromate oxidizing agents, hypochlorous acid is

question

Add sodium bisulfite, NaHSO3.

answer

Sodium hypochlorite and glacial acetic acid combine to make hypochlorous acid. Hypochlorous acid oxidizes cyclohexanol to cyclohexanone. At the end of the reaction, any excess hypochorous acid must be destroyed. How is the destruction of HOCl accomplished?

question

we added bleach dropwise into a flask containing acetic acid

answer

In the oxidizing secondary alcohols experiment, how did we generate the oxidizing agent?

question

we touched a drop of the reaction mix onto a piece of KI-starch paper

answer

In the oxidizing secondary alcohols experiment,how did we test for the precense of the oxidizin agentt?

question

we placed the reaction flask in an ice water bath

answer

In the oxidizing secondary alcohols experiment,How did we control the rate of reaction?

question

we combined the organic layer over anhydrous potassium carbonate

answer

In the oxidizing secondary alcohols experiment,how did we dry the reaction product?

question

True

answer

Hypochlorous acid is an oxidizing agent.

question

true

answer

Concentrated acetic acid is corrosive.

question

false

answer

Methylene chloride is flammable.

question

true

answer

Methylene chloride is a probable human carcinogen.

question

false

answer

Pipets that contain only water can be disposed of in the trash.

question

SN1 reaction in which formation of tertiary carbocation is the rate determining slow step.

answer

The preparation of 3‐chloro‐3,7‐dimethyloctane from 3,7‐dimethyl‐3‐octanol, is an:

question

your compound is impure

answer

Your experimentally determined melting point is 10 degrees low and has a 4 degree melting point range. This indicates that:

question

1700cm-1

answer

Benzoic acid and phenol can be differentiated in the infrared because benzoic acid shows an absorption near ______ and phenol does not.

question

more of the more volatile component

answer

In the fractional distillation of an ideal solution of two miscible liquids, the vapor contains:

question

CaSO4

answer

Which reagent is not an oxidizing agent? NaOCl K2Cr2O7 KMnO4 CrO3 CaSO4

question

2;180

answer

. An sp carbon typically has ___ atoms attached to it with bond angles of about __

question

The functional group was an amine and the reagent was an acid

answer

During the extraction lab you extracted benzocaine out of CH2Cl2. What was the reactive functional group and what reagent was used to make this happen?

question

ally 2‐naphthyl ether

answer

At the end of the phase transfer catalysis experiment, what molecule had the highest Rf value when you ran the TLC?

question

second order

answer

The rate law: rate = k[RCl][‐OH] is representative of what type of kinetics?

question

silver nitrate test

answer

.Which one of the following tests cannot be used to detect the presence of eugenol? a. ferric chloride test b. Baeyer test c. bromine test d. silver nitrate test e. b and c

question

Adding a polar solvent causes the Rf of the compound to increase.

answer

.In reference to TLC, which statement best describes the change in Rf caused by a change in solvent polarity?

question

the peak overlap increases and becomes unacceptable

answer

In preparative gas chromatography, as the amount of sample injected increases

question

.small crystals form that have a large surface area on which impurities will be adsorbed.

answer

When the solution is cooled very rapidly in recrystallization

question

d.At the eutectic point, the melting point of a mixture of two compounds is sharp.

answer

Which of the following is true about melting point determination? a.At the melting point of a substance, the solid and vapor states exist in equilibrium. b.An impure compound has a narrow, sharp melting point range. c.A solid is said to sublime when it first liquefies and then vaporizes to a gas. d.At the eutectic point, the melting point of a mixture of two compounds is sharp. e.Although a substance may exist in different crystalline forms, it has only one characteristic melting point.

question

a. the portion of the spectrum from 1500‐400 cm‐1 that is unique for nearly every compound

answer

The fingerprint region of the IR refers to:

question

c. 74%

answer

You have treated 10.0 g of 2‐methyl‐2‐butanol (MW = 88.15; density = 0.805 g/mL) with concentrated HCl and purified the product by extraction and distillation. Your product is 9.0 g of 2‐chloro‐2-methylbutane (MW = 106.60; density = 0.865 g/mL). The percent yield is:

question

e. an oxidation

answer

The reaction that converts 2‐heptanol to a carbonyl compound is best described as:

question

e. sp3 and 109.5°

answer

What is the hybridization of the oxygen atom and the approximate bond angles around oxygen in methanol, CH3OH?

question

Acetone is soluble in water.

answer

According to the Merck Index, the amount of solvent necessary to dissolve 1.0 g of m‐nitrobenzoic acid is: water ‐ 146 mL, ethanol ‐ 3 mL, chloroform ‐ 220 mL, ether 4.5 mL, acetone ‐ 2.5 mL. Why wouldn't acetone be the best solvent to extract m-nitrobenzoic acid from water?

question

thin layer chromatography

answer

In the phase transfer catalysis experiment, what type of analysis was used to determine the progress of the reaction?

question

H2O

answer

In the kinetic study of SN1 solvolysis, the nucleophile in the reaction is?

question

Concentration of nucleophile affects the rate of the reactions

answer

What is the similarity with E2 elimination and SN2 substitution?

question

...

answer

Look at problem #23

question

the collection tube must be uncapped to allow free passage of vapor through the tube

answer

When performing preparative gas chromatography

question

...

answer

look at number 25

question

base extraction

answer

In "Who Has My Compound," the lab included a solubility test for the unknown compounds in sodium bicarbonate. What purification technique uses the same chemical properties as the solubility test?

question

e.A thick layer (> 10 ) of sample is required to run ATR‐IR.

answer

Which of the following statements concerning the infrared spectroscopy experiment is WRONG? a. ATR stands for "attenuated total reflectance". b.ZnSe is the most commonly used crystal for ATR. c.Normal IR spectra show absorptions around 400‐4000 cm‐1 .d. Absorptions below 1500 cm‐1 are usually considered as the fingerprint region. e.A thick layer (> 10 ) of sample is required to run ATR‐IR.

question

e. a, b and c

answer

The technique of simple distillation: a. can be used as a means of separation b. can be used as a means of purification c. is based upon differences in boiling points of two substances d. a and b e. a, b and c

question

The appearance of a peak at approximately 1700 cm‐1 and disappearance of broad peak at approximately 3300 cm‐1 .

answer

30.When analyzing the IR of your product from the Oxidation of a Secondary Alcohol you were looking for what in the spectra?

question

the concentration of the sample

answer

Retention time in gas chromatography is not affected by:

question

...

answer

figure out number 32

question

...

answer

figure out number 33

question

a. Carbocation intermediates are common in E2 elimination reactions.

answer

The reaction performed in the dehydrohalogenation experiment was an E2 reaction. Which of the following statements about E2 reactions is false? a. Carbocation intermediates are common in E2 elimination reactions. b. E2 reactions are stereospecific. c. Strong bases encourage elimination reactions. d. It is easier to perform an E2 reaction on an alkyl chloride than an alkyl fluoride. e. Tertiary alkyl halides will undergo faster elimination than secondary alkyl halides.

question

c. The OH‐ removes the phenolic hydrogen. The eugenol salt will be found in the top layer.

answer

. In the extraction of eugenol from clove oil, the clove oil is treated with NaOH. Two layers form, an aqueous phase and a methylene chloride phase. Which of the following statements is true? a. The OH‐ cleaves the ether bond. The eugenol molecule will be found in the top layer. b. The OH‐ cleaves the ether bond. The eugenol molecule will be found in the bottom layer. c. The OH‐ removes the phenolic hydrogen. The eugenol salt will be found in the top layer. d. The OH‐ removes the phenolic hydrogen. The eugenol salt will be found in the bottom layer. e. The OH‐ nucleophilically adds to the double bond. The derivative will be found in the lower layer.

question

e. a, b and c

answer

for the selection of an appropriate solvent in thin layer chromatography one must consider: a. polarity of absorbent b. polarity of solvent c. polarity of compounds, if known d. b and c e. a, b and c

question

b. methyl groups are diequatorial

answer

Which of the following variations of 1,2‐dimethylcyclohexane in the chair conformation is the most stable? methyl groups are diaxial b. methyl groups are diequatorial c. methyl one is axial, methyl two is equatorial d. methyl one is equatorial, methyl two is axial e. all are equally stable since it is in the chair conformation

question

c. water

answer

Which of the following is the most polar compound? a. acetone b. acetic acid c. water d. toluene e. cyclohexane

question

lower and has a wider range

answer

The melting point of an impure compound is (than) the corresponding pure compound.

question

2,3,4

answer

A strong IR absorbance in the 1670‐1830 cm‐1 range is present in which of the following: 1. alkenes 2. esters 3. aldehydes 4. carboxylic acids 5. alcohols

question

E. a,b,c

answer

Before returning your bin of glassware to the stockroom, you are required to rinse the glassware with acetone to: a. insure that all traces of water have been removed b. insure that no traces of organic soluble material has remained in the flasks c. insure that no unwanted reaction will occur the next time the glassware is used, owing to the presence of a contaminant d. a and b e. a, b and c

question

removing the remaining acid

answer

In the preparation of 3‐chloro‐3,7‐dimethyloctane, the organic layer was washed with sodium bicarbonate solution. This washing was for the purpose of:

question

acetone, ethyl acetate, benzene

answer

You inject a mixture of these three compounds on a non‐polar column: acetone, bp 56 C; ethyl acetate, bp 77 C; benzene, bp 80 C. Order the three compounds by increasing retention time.

question

dichloromethane

answer

Most organic compounds are less dense than water and will be on top of the aqueous phase in a separatory funnel. Which of the following organic phases breaks this rule and will be on the bottom? a. hexane b. ether c. dichloromethane d. ethyl acetate e. toluene

question

the rate would be unchanged

answer

. A student's kinetic study of the SN1 solvolysis reaction of 1‐phenyl‐1‐chloroethane (using dilute NaOH to neutralize the HCl formed) gave a rate constant k=5.0 x 10‐4 sec‐1 , using a 70% H2O, 30% ethanol mixture for solvent. What effect would doubling the base concentration have on the rate constant?

question

water insoluble oils

answer

Steam distillation is used to isolate:

question

Thermal conductivity detector

answer

What type of detector is used in the GC instruments used in the A&M Organic Labs?

question

slightly soluble at low temperature and highly soluble at high temperature

answer

A compound to be recrystallized should be:

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