KeJoSaBe

Hi, thanks so much for this response! It helped to jog my memory a bit. My student is is taking a 2nd year undergrad class in organic chemistry (2nd of 2 classes). He has gone through the following reactions: 1. substitution of alkyl halides, alcohols etc. 2. Elimination of alkyl halides, alcohols etc. 3. Electrphilic/concerted addition of alkenes and alkynes. 4. Free radicals: substitution and addition 5. Electrophilic aromatic substitution reactions of benzene and its derivatives. One big question that I have is how to form a 5 membered ring. My initial thought was Diels-Alder but, upon review of my notes I see this forms 6 membered rings. On the other hand, I am going through old notes trying to see if there is a way to convert benzene into a 5 membered ring.

I took organic chemistry about 7 years ago and did fairly well. So, I thought I would be able to help tutor a university student even though I haven't done it since that time; however, we are getting into chemical synthesis and I am starting to realize that there is a lot I don't remember. Can anyone point me in the right direction here? The student has to synthesize the following chemical compound (I have attached the image to this message). We must start with organic reagents no larger than 2 - 3 carbons, or benzene. Any inorganic reagent can be used. Any help is appreciated! Thanks

Thanks for spending the time on this studiot, I really do appreciate it! The following is the question verbatim: "A 700 kg Piston is initially held in place by a removable latch inside a horizontal cylinder. The totally frictionless cylinder (assume no viscous dissipation from the gas also) has an area of 0.1 m^2; the volume of the gas on the left of the piston is initially 0.1 m^3 at a pressure of 8 bars. The pressure on the right of the piston is initially 1 bar, and the total volume is 0.25 m^3. The working fluid may be assumed to follow the ideal gas equation of state. What would be the highest pressure reached on the right side of the piston and what would be the position of the piston at that pressure? (a) assume isothermal; (b) What is the kinetic energy of the piston when the pressures are equal? (partial answer 1.6 bars)" I am starting to think that the answer given at the end of the question is incorrect. I cannot reproduce this not matter how I try to...a maximum pressure of 1.6 bar in the right hand chamber simply makes no sense, based on the given information. Also, After further review of my work in post #10 I realize there is a mistake in my original energy balance. Where I have PE (which is meant to represent change in potential energy) = Ws = 80,000*ln(VL2/0.1) - 15,000*ln((0.25-VL2)/0.15). This equation is true but, I failed to realize at the time that the change in PE from the initial state to the final state (i.e. the point at which the piston is furthest the to the right it can go...where KE=0 and PE2=PE1) is 0. I realized this after reading over your explanations...thanks again! Therefore, my equation above Should be PE = 0 = Ws = 80,000*ln(VL2/0.1) - 15,000*ln((0.25-VL2)/0.15). With this in mind, I can easily calculate the volume of the left hand chamber by trial and error (ends up being 0.2488 m^3). THis implies that the volume of the right chamber at this point is 0.0012 m^3 and from the ideal gas law, the pressure at this point is 125 bar......seems like a lot but, it makes a lot more sense to me than the answer given in the book. For part (b) I simply PE1 = KE = Ws = 80,000*ln(VL2/0.1) - 15,000*ln((0.25-VL2)/0.15) where the initial KE is equal to 0. VL2 (Volume of the left hand side) can be found based on the information supplied and the fact that PL = PR. Hopefully this makes sense.

I agree with your assessment of the situation in your comments, however; I am not quite sure how to incorporate the oscillatory portion. I agree that to calculate the point where the chamber pressures are equal should be straight forward (however, I see that I calculate a value of 3.8 bars when chamber pressures are equal but, the book gives a final answer of 1.6 bars for the highest pressure in the right chamber).......so, I am still confused..

My apologies for not keeping track of this post sooner. I appreciate all of the responses and effort put into this question! I will try and explain my approach to this problem. Studiot, I reviewed my energy balance and agree that the kinetic energy term in my original equation is not needed here. My energy balance has become dPE = dWs where, PE and Ws are explained in my original post. dWs = PLdVL - PRdVR = nRTL/VLdVL - nRTR/VRdVR (2) where PL and VL are Pressure and Volume of the Left hand chamber while PR and VR are Pressure and Volume of the Right hand chamber. Since this is an isothermal process, PLVL = constant at any point and is actually 800,000 N/m^2*0.1m^3 = 80,000 N*m (or Joules). Same can be said of PRVR = constant = 100,000 N/m^2*0.15m^3 = 15,000N*m (J). From the Ideal Gas Law nRTL = 80,000 J while nRTR = 15,000 J (Since this is an isothemal process) Then, dWs = 80,000/VL*dVL – 15,000/ VR*dVR And, PE = Ws = 80,000*ln(VL2/VL1) - 15,000*ln(VR2/VR1) But, since we already know VL1 = 0.1 m^3 and VR1 = 0.15 m^3 (Assuming the thickness of the piston has been taken into account when the question said the total volume of the cylinder is 0.25 m^3…I am assuming that is the total open space volume) PE = Ws = 80,000*ln(VL2/0.1) - 15,000*ln(VR2/0.15) And since we know that VL+VR = 0.25 m^3, then VR2 = 0.25 -VL2 and the equation becomes PE = Ws = 80,000*ln(VL2/0.1) - 15,000*ln((0.25-VL2)/0.15)… Now, I have 2 unknowns PE, and VL2. This is where I am stuck…..if I can get the Potential energy associated with this then I can calculate VL2 which will allow me to calculate the position of the piston and Pressure (from the ideal gas law)……This is what I have done so far…please feel free to show me any mistakes in my thinking or, on the other hand what I might do to calculate the PE…seems I need to know the final position of the piston before I do that…..I will try to respond in a more timely manner this time around! Thanks!

Ok, I need help setting up the energy balance for the following problem: I have a horizontal frictionless piston-cylinder device in which both sides of the piston are enclosed (i.e. no side is open to atmosphere). Assume no viscous dissipation from the gas also) Piston is initially held in place by a removable latch (imaginary) within the cylinder. Initial conditions given on the left side of the piston is P = 8 bar, V = 0.1 m3 Initial conditions given on the right side of the piston is P= 1bar Total Volume of the cylinder is 0.25m3 Fluid follows ideal gas EOS Piston is 700 kg Cross sectional area of the piston is 0.1 m2 No information is given on the temperature of the system or the surroundings other than to say we can assume this is an isothermal process Question: When the latch is released, and the piston is free to move, what is the highest pressure reached on the right side of the piston and what would be the position of the piston at that pressure? Initially, I took the piston itself as the system and performed a closed system energy balance on it. Doing that, I get the following: dKE+dPE = dWs where KE is the kinetic energy of the piston as it moves, PE is potential energy of the piston and Ws is the work done at the boundary of the piston due to expansion/contraction of the gas on either side of the piston. From here, I am getting lost in the details of this problem and I am starting to wonder if my basis is off. I just need a bit of help getting this started. Thanks! FYI - this question is actually from Elliott and Lira's Introductory Chemical Engineering Thermodynamics 1st edition P2.19 if you have the book