Quiz 3 Winter 2017

[BrianaBarr2A]

for #1, why do we need "iso" infant of propyl? wouldn't the 4- signify the branching?

This is because "iso" identifies that there is 2 CH3's coming off of 1 CH (in all there is 3 carbons so prop). That is what CH(CH3)2 means so iso is used and it is connected to the 4th carbon and there are 10 carbons with single bonds so the the name is 4-isopropyl-decane

[BrianaBarr2A]

how would you draw out 2-butene or anything with a number in front of it ???

For 2-butene the number identifies where the double bond is located since butene (the -ene means a double bond) so it is located on the second Carbon. For anything else with a number in front of it, it just means what carbon it is located on and the number is associated with whatever is directly after it in the name.

[ariana_cruz_1C]

Why is the answer for number 4, 4-butyl-1,2-dimethylcyclohexane and not 1,butyl-3,4-butylcyclohexane?

remember we want to start numbering wherever we could get the lowest number, so in 4-butyl-1,2-dimethylcyclohexane (4+2+1 gives us 7) whereas 1,butyl-3,4-butylcyclohexane (4+3+1 gives us 8)

[Annie Zhang_ 3C]

for #1, why do we need "iso" infant of propyl? wouldn't the 4- signify the branching?

I believe the iso- indicates a structural connectivity of (CH3)2CH- , as indicated in page 9 of the Ochem green booklet.

[Minu Reddy]

Can someone please help me to understand when to use iso-, neo-, sec-, and tert, when doing IUPAC naming?

Thank you

[Ariana de Souza 4C]

for #1, why do we need "iso" infant of propyl? wouldn't the 4- signify the branching?

No, because the 4 signifies from what carbon on the MAIN BRANCH you're substituent is on. WIthin the substituent itself, though, there is branching, and that's why you'd either say iso-propyl (common name) or maybe 1-methyl-ethyl (IUPAC)

[SydneyKusumoputro_3K]

Could someone help me understand the thought process behind #7?

[Molika Soben_3J]

Why is the answer for number 4, 4-butyl-1,2-dimethylcyclohexane and not 1,butyl-3,4-butylcyclohexane?

When naming, once you get a lower number, then that's it. Since 2 is smaller than 3, then the name of the compound should be the one that includes the 2, not the 3.

[Mizuno_Mikaela_1D]

how would you draw out 2-butene or anything with a number in front of it ???

The 2 means the carbon carbon double bond starts at carbon 2 (between the second and third carbon) so it would be CH3-CH=CH-CH3.

[Vandan_Patel_3L]

how would you draw out 2-butene or anything with a number in front of it ???

The 2 in two butene means that there is a double bond as it ends in "en" and the double bond is between Carbon 2 and 3.

[Vandan_Patel_3L]

Can someone explain when to use tert vs neo and sec vs iso please?

[AlexandraOsterland_3E]

For the quiz will we have to know how to draw transition states? Or will just drawing the arrows for each step in the reaction suffice?

[Yinhan_Liu_1D]

#2, it asks us to draw a structure, when we are drawing the line structure, do we specify (draw out) the carbon where the parent chain is branched? Or we just draw a branch?

[Ethan_Kato_1D]

For number 5, how are there 2 intermediates?

[TiengTum2D]

how would you draw out 2-butene or anything with a number in front of it ???

Remember that 'ene ' just means that it has double bonds and the number indicates on which carbon the double bond is being located. What u can do first is to write out all carbons, place the double where needed and fill it out with hydrogens. Hope this helps!

[Natalie Hunt 1E]

For the quiz will we have to know how to draw transition states? Or will just drawing the arrows for each step in the reaction suffice?

I believe we will need to know how to draw transition states. I was at a UA session today, and we went over transition states and how to draw them.

[Corey Switzler 2L]

Where can we find the answers to practice quiz 3?

[Corey Switzler 2L]

Also, since we're only covering alkanes and cycloalkanes on quiz 3, does that mean some of the types questions of practice quiz 3 won't be on the real quiz?

[Natalie Hunt 1E]

Where can we find the answers to practice quiz 3?

The answers to the quiz are posted at the beginning of this thread.

[Armani Dodson 1A]

On one of the examples in the course reader the naming says "tert" do you know why that is?

[604746385]

Tert refers to tertiary carbon meaning it is connected to 3 other carbons

[Madison_Moore_1I]

Is quiz 3 going to be more focused on naming organic compounds rather than kinetics?

[MariaReina_Garcia_3E]

how would you draw out 2-butene or anything with a number in front of it ???

The -ene refers to a double carbon bond, while the 2 refers to the carbon in which the double bond begins. Therefore 2-butene will be c-c=c-c

[Korosh Bahrami]

Does anyone know how to do #11 on the Quiz 2 Preparation in the Course Reader?

[Chem_Mod]

Is quiz 3 going to be more focused on naming organic compounds rather than kinetics?

See earlier post in this thread and please read what I posted on Saturday:
"Your Quiz 3 covers more Kinetics."

[Rachelle_Stark_3H]

Where do I find the answers to the quiz 3 preparatory quiz??

[Natalie Hunt 1E]

Where do I find the answers to the quiz 3 preparatory quiz??

Dr. Lavelle posted the quiz 3 answers towards the beginning of this thread.

[Logan 3C]

how would you draw out 2-butene or anything with a number in front of it ???

The 2 in 2-butene signifies that the location of the double bond is after the second carbon. So you would draw this as a normal butene, just with the double bond after the 2nd carbon. In other cases, you would draw either the substituents or the double/triple bonds based on the carbon number given.

[Morgan Zapasnik 1N]

For question number 2, can someone explain how ethyl & methyl are on the 3rd carbon? And what does it mean by the third carbon in the hexane line structure? A description or picture would be greatly appreciated!

[sophianguyen_1N]

for #1, why do we need "iso" in front of propyl? wouldn't the 4- signify the branching?

No, the 4 only denotes which carbon the substituent is attached to. If we did not use iso, the naming of the substituent would be completely different.

[stephanieyang_3F]

for #1, why do we need "iso" in front of propyl? wouldn't the 4- signify the branching?

4 signifies that there's a substituent on the 4th carbon of the chain and the reason you put isopropyl instead of propyl is because it's not a straight alkyl substituent CH2CH2CH3, but rather CH(CH3)2. How you can distinguish the two is that for CH(CH3)2 there's a parentheses which signifies that they are both substituents of CH.

[K Phelan 3D]

how would you draw out 2-butene or anything with a number in front of it ???

We have not yet learned how to draw alkenes, which 2-butene is as seen by its infix. This won't be needed for quiz three. (The two shows where the double bond is)

[Preet_Bains_1D]

for #1, why do we need "iso" in front of propyl? wouldn't the 4- signify the branching?

The "iso" signifies that it is CH(CH3)2 instead of CH2CH2CH3. If the substituent was CH2CH2CH3 then the answer would be 4-propyldecane.

[Preet_Bains_1D]

For number 5, how are there 2 intermediates?

Look in the course reader on page 84 and 85. It has an example of the same mechanism.

[Chem_Mod]

Can someone explain when to use tert vs neo and sec vs iso please?

A good summary can be found here: http://web.chem.ucla.edu/~harding/IGOC/ ... _name.html
And in your organic textbook.

TLDR: Tert- where the functional group is bound is at a carbon bonded to 3 other carbons.
Neo- All except for 2 carbons are in a continuous chain, where those 2 extra carbons form a terminal tert-butyl group.
Sec- Mostly relevant for 4 chain carbons. Functional group is bound to a secondary carbon (a carbon that is attached to 2 other carbons)
Iso- All except for 1 carbon is part of the main chain.

[Chem_Mod]

For question number 2, can someone explain how ethyl & methyl are on the 3rd carbon? And what does it mean by the third carbon in the hexane line structure? A description or picture would be greatly appreciated!

[Rika Jitosho 2E]

for #1, why do we need "iso" in front of propyl? wouldn't the 4- signify the branching?

If you draw out the structure, you'll see the branching of (CH₃)₂CH, which is how you know to include the prefix iso-. By that same logic, if the branching had (CH₃)₃C, you would use the prefix neo- but only with five or more carbons. See lecture notes and Introduction to Organic Chemistry.

[andrea mejia]

For number 5, how do we know the first step is the slow one?
Also, could someone explain when and how to use iso- in naming? Or just how to do #1?

[Imani Johnson 1H]

For iuPac naming, when dealing with a cycloalkane, how do you determine which molecule to number as #1, say the cycloalkane has two substituents...for example, a cyclohexane with substiuents of CH3 and Br?

[Chem_Mod]

For iuPac naming, when dealing with a cycloalkane, how do you determine which molecule to number as #1, say the cycloalkane has two substituents...for example, a cyclohexane with substiuents of CH3 and Br?

If your substituents are not functional groups, then you would number it whichever way gives you the lowest set of numbers. If one of your substituents is a functional group, then that will take priority in numbering. In the example you mentioned, bromo- comes before methyl- so the bromine would get the smaller number.

[104469125]

On page 83: electrophilic addition of Hbr to 2-Butene
Could we have the positions of Br and H switched for the final answer?

[Chem_Mod]

On page 83: electrophilic addition of Hbr to 2-Butene
Could we have the positions of Br and H switched for the final answer?

Yes. We will not give you examples in which the final placement of Br and H will matter. As you take more organic chemistry, you will learn that there are rules which govern which carbon bonds to the Br and which bonds to the H.

[104469125]

For number 5, how do we know the first step is the slow one?
Also, could someone explain when and how to use iso- in naming? Or just how to do #1?

I was also wondering the same thing. How do we know that the first step is the rate limiting step? Does it have to do with the intermediates in step 1?

[Caity Colt 2N]

For number 5, how do we know the first step is the slow one?
Also, could someone explain when and how to use iso- in naming? Or just how to do #1?

For 5, the first step is the slow one because it involves breaking two bonds (Carbon-carbon double bond and the H-Br bond). Step two only involves the bond forming between carbon and Br.

For 1, the parent chain would be decane, since there are 5 carbons. The substituent, CH(CH3)2 would be named isopropyl because iso is used to describe the structural pattern (CH3)2CH-- and there are four carbons (meaning it is propyl). Since (counting from right to left) the substituent is on the fourth carbon.

[Emma Cole 3F]

How do you know when to add "iso" when naming compounds?

[Audrey_Hall_2I]

Does anyone know good kinetics problems to do in preparation for the quiz? Thanks!

[RitaChang_2C]

For number 5, how do we know the first step is the slow one?
Also, could someone explain when and how to use iso- in naming? Or just how to do #1?

I was also wondering the same thing. How do we know that the first step is the rate limiting step? Does it have to do with the intermediates in step 1?

Step one is the rate limiting step as it is slower. In the first step you need to break two bonds and form one, whereas in step two you only need to form one bond.

[Ashley Curtis 2O]

for #1, why do we need "iso" infant of propyl? wouldn't the 4- signify the branching?

This is because "iso" identifies that there is 2 CH3's coming off of 1 CH (in all there is 3 carbons so prop). That is what CH(CH3)2 means so iso is used and it is connected to the 4th carbon and there are 10 carbons with single bonds so the the name is 4-isopropyl-decane

How is this different from regular propyl?

[KarinaOropeza_2L]

Shouldnt number 4 be 5-butyl instead of 4-butyl?

You have to go in the direction that gives you the lowest numbers. So in this case you would go counterclockwise.

[Rachel_Harland_3I]

for #1, why do we need "iso" in front of propyl? wouldn't the 4- signify the branching?

Its isopropyl because its CH(CH3)2 and not CH3(CH2)2 which would be propyl. as a rule of thumb, the two CH3 indicates iso

[KarinaOropeza_2L]

Shouldnt number 4 be 5-butyl instead of 4-butyl?

You have to go in the direction that gives you the lowest numbers. So in this case you would go counterclockwise.

[Banik_Housepian_2K]

Would vinyls be considered functional groups and therefor we don't need to know it for Quiz 3?

I had this question as well, but im pretty sure it wont be on the quiz.

[Maya Kandah 3M]

Does anyone know good kinetics problems to do in preparation for the quiz? Thanks!

I would recommend the book problems from chapter 15

[Chris_Rudewicz_3H]

We still get to drop our lowest quiz score, right?

[Chris_Rudewicz_3H]

So if we have say, for example, a 35/40 on quiz 1, a 37/40 on quiz 2, and then we get a 10/40 on quiz 3, what will happen is we will get a 37/40 on quiz 3 in the gradebook?

[Nikhita_Jaaswal_2H]

for #1, why do we need "iso" in front of propyl? wouldn't the 4- signify the branching?

You have to place "iso" in front for the propyl because 4 signifies where the propyl is connected to the decane, not the branching on the propyl substituent itself.

[Chem_Mod]

So if we have say, for example, a 35/40 on quiz 1, a 37/40 on quiz 2, and then we get a 10/40 on quiz 3, what will happen is we will get a 37/40 on quiz 3 in the gradebook?

Yes

[Jocelyn Sandoval 3B]

For the quiz 3 preparation, why does electrophilic addition have 2 intermediates? Graphically, isn't there only 1?

[BetcyGaspar_3C]

For the quiz 3 preparation, why does electrophilic addition have 2 intermediates? Graphically, isn't there only 1?

Pages 84-85 of the course reader demonstrate the graph of the problem in quiz 3 preparation. Just because there is only one dip in the graph does not mean it stands for one intermediate.

[EmilyLeibovitch2E]

Is it correct that electrophilic addition always has 2 intermediates where SN2 only has 1?

[Leila_Shamir_3J]

For number 5 in the practice quiz, is the reaction an electrophilic addition reaction because the hydrogen is being added to the bromide molecule?

[Leila_Shamir_3J]

On number 7 on the practice quiz, why does the butene become butane after the addition of Cl2?

[Natalie Rotstein 3J]

The quiz 3 prep includes alkenes and cycloalkenes, and Lavelle's responses to questions on the quiz prep problems seem to imply that we are expected to know how to solve all of the problems in the quiz prep, but the beginning of the thread it says alkanes and cycloalkanes in the textbook and only up to pg 96 (prior to the start of alkenes) in the course reader - do we need to know how to solve problems involving alkenes or not?

[Chem_Mod]

Is it correct that electrophilic addition always has 2 intermediates where SN2 only has 1?

SN2 does not have any intermediates. Perhaps you meant transition states.

Electrophilic addition has 2 transition states and SN2 has 1. Correct.

Ask me after class if this is not clear.

[Chem_Mod]

On number 7 on the practice quiz, why does the butene become butane after the addition of Cl2?

Because it no longer has a double bond.

[Chem_Mod]

The quiz 3 prep includes alkenes and cycloalkenes, and Lavelle's responses to questions on the quiz prep problems seem to imply that we are expected to know how to solve all of the problems in the quiz prep, but the beginning of the thread it says alkanes and cycloalkanes in the textbook and only up to pg 96 (prior to the start of alkenes) in the course reader - do we need to know how to solve problems involving alkenes or not?

"Lavelle's responses to questions on the quiz prep problems seem to imply that we are expected to know how to solve all of the problems in the quiz prep"

I explicitly stated in the quiz 3 prep answers above:
"Q3. Alkenes not covered in your Quiz 3."

Q3 was an alkene structure and we covered these structures and names (geometric isomers, cis/trans, E/Z) this week (which is not on quiz 3).

Your question is also ambiguous. Do you mean alkene structures, cis/trans, etc. The answer is again no, not for quiz 3.

If you mean electrophilic addition across a double bond which I covered three times for an entire lecture last week. Yes. A double bond is an alkene. One cannot cover the electrophilic addition (across a double bond) reaction mechanism and not have an alkene in the reaction.

[Natalie Rotstein 3J]

Thank you for clarifying, I was mainly confused about whether we would need to know alkene structures/formulas from the name for alkenes other than the ones mentioned in lecture in the context of the electrophilic addition, such as ethene and 2-butene, but I think I understand what we need to know now. Essentially, we need to know how alkenes function in an electrophilic addition reaction, and whether they are electrophilic or nucleophilic, as well as some specific alkene-involving-reactions discussed in lecture, but for the most part, we don't need to know the IUPAC naming of alkenes or the structure based on their names?
Thanks!

I explicitly stated in the quiz 3 prep answers above:
"Q3. Alkenes not covered in your Quiz 3."

Q3 was an alkene structure and we covered these structures and names (geometric isomers, cis/trans, E/Z) this week (which is not on quiz 3).

Your question is also ambiguous. Do you mean alkene structures, cis/trans, etc. The answer is again no, not for quiz 3.

If you mean electrophilic addition across a double bond which I covered three times for an entire lecture last week. Yes. A double bond is an alkene. One cannot cover the electrophilic addition (across a double bond) reaction mechanism and not have an alkene in the reaction.

[nicoleclarke_lec1M]

how would you draw out 2-butene or anything with a number in front of it ???

This is an alkene and it would be a 4-carbon molecule with a double bond between the 2nd and 3rd carbon.

[Milan Hirpara 3K]

What are the units for A in the Arrhenius equation?

[Chem_Mod]

What are the units for A in the Arrhenius equation?

Great question.

In the Arrhenius Equation A has the same units as k (the rate constant).

This makes sense since one can obtain A from the y-intercept in the ln k vs 1/T plot where the y-intercept is ln A.


Note that the units of k are dependent on the order of the reaction.

[404639305]

Will we have to know tert and sec for the quiz or can we use the IUPAC names for them instead of common names?

Lavelle said that he would never explicitly ask for common names, he said he with either just ask for the name (in which case you have the option of IUPAC or common) or just eh IUPAC.

[404639305]

Why is the answer for number 4, 4-butyl-1,2-dimethylcyclohexane and not 1,butyl-3,4-butylcyclohexane?

remember you name in alphabetical order

[Arie Hakimi 1L]

will the answers to the quiz be posted?

[Chem_Mod]

will the answers to the quiz be posted?

I posted the answers to Quiz 3 Preparation on March 4th. See answers above.

[Coleen_Leslie_2L]

Will quizzes be returned in discussion sections this week?

[Chem_Mod]

Will quizzes be returned in discussion sections this week?

Yes

[tpat14]

If a a reaction is at equilibrium is it always the limiting reactant because it's slower? Or is it faster and the other is limiting?

[TiengTum2D]

how would you draw out 2-butene or anything with a number in front of it ???

In that case, the 2 simply indicate the location of the double bond. So the double would be between the 2nd and 3rd carbon in your carbon chain drawing.

[vannahyazon 1L]

We still get to drop our lowest quiz score, right?

Your lowest quiz score will be replaced by your highest quiz score.

So your grade for quizzes should be:

1. HIGHEST SCORE
2. HIGHEST SCORE
3. MIDDLE SCORE

[Samantha Rubin-Pope - 1H]

When will our quiz 3 scores be posted to MyUCLA?

[veeksha25]

Iso is needed whenever you have a methyl connected to "two carbons" (methyl connected to a carbon which is connected to another carbon)

[Armani Dodson 1A]

Where are the answers for the actual quiz 3 posted.

[Armani Dodson 1A]

How do you get the pseudo equilibrium constant on quiz 3?

[Diana_Anum1G]

How do you get the pseudo equilibrium constant on quiz 3?

Transition state over reactants.