For a dehydration reaction, how do you know which carbons in the molecule will form the double bond? (The carbon bearing the OH-group, and the next carbon. - GS).

For thermal cracking, simply stated, the process is essentially flash heating (It will work. - GS) and then rapidly cooling the substance so that the compound separates? (No. It is to prevent further decomposition to carbon. To separate, distillation must follow. - GS).

Dr. Sereda, can you explain why sometimes the cis-trans terminology fails to describe certain stereoisomers? (Because sometimes you do not know at which substituents to look, so you need rules for prioritizing them, which is E-Z- nomenclature. - GS).

The relative density of a polymer is due to branching factors mainly, right? So would it be correct to assume that thicker materials such as thick plastic sheets (for example) would be due to a polymer that is less branched (aks more “linear” of a structure) (Yes. - GS). whereas the plastic for packaging is more branched making it more flexible? (Flexibility is mostly determined by conformational mobility. - GS). Just out of curiosity, how would you go about manipulating this concept, so that you could produce a compound of desired density? (In industry, radical-induced polymerization of ethylene causes the radical centers hopping along the chain, which causes branching. Polymerization directed by a metal (Ziegler-Natta catalyst), produces mostly linear chains. An extreme example of this type of manipulation is making aerogels in supercritical carbon dioxide. - GS). Meaning if I were to say add heat to the compound/ substance the material would become more flexible? (Yes, which is why under freezing temperatures, some plastics and rubbers become inflexible, fragile, and may fall apart. It is a big issue for aircraft landing gear and spaceships. - GS).

Rate limiting step is that determined by the step with the highest Transition state only or is it the largest difference between the minima (intermediate) and the transition state that determines the rate limiting step? (The difference between the transition state and the preceding intermediate or starting material determines the activation energy and, therefore, the reaction rate. - GS).

Am I correct in thinking that alkenes are the only compounds that can be labeled cis or trans since alkanes can rotate around the single C-C bond and alkynes can only bind to one other substituent on either side?  (No. Cyclic compounds also can be cis- or trans- - GS).

Did you say that trans is typically more stable than cis ? (Yes, if there is no attraction between the substituents. - GS). if so would the same apply for Z configuration in terms of it being more stable than E? Thanks (There is no trend. It all depends on the repulsion and attraction between specific substituents. - GS).

When determining the strength of bases does the double and triple bond making the base stronger or weaker than a base with a single bond? Thank you (It make the base weaker due to a lowering energy as we go from sp3 to sp-hybrid orbital. - GS).

Would the acid base formula usually go Base + Acid → X? (It is typical for Lewis acids and bases - GS). And it would always go Base + Acid ←→ Acid + Base? (It is typical for Bronsted acids and bases. - GS).

Just to make sure I am understanding this correctly the curved arrow notation provides info on Redistribution of electrons and charges between the nuclei, right? (Yes, you are right on target. - GS).

Most of an acid is ionized when pH is larger than pKa, so would practically none of the acid be ionized if the pka was larger than the pH? And then about half would be ionized when the pH and the pKa are roughly equal? (Correct. - GS).

Would be correct to affirm that a ph-7.4 is half ionized? (Yes for acids with pKa = 7.4 - GS) To be half-ionized shouldnt be a ph=7? (Yes for acids with pKa = 7 - GS).

Would NH3+ be the conjugate base to H3O+ (the acid) in this example because H3O+ donates a H+ to produce NH3+? (No. H2O is the conjugate base to H3O+, because when H3O+, loses H+, it becomes H2O. The other pair is NH3 / NH4+ - GS).

I thought amines were classified as basic? (They can be both basic because of the lone electron pair, and acidic because of the N-H bond. It is called “amphoteric. - GS).

Could you go over principal chain once more? (For alkanes, it is the longest carbon chain with the largest number of substituents. - GS).

Would you say that 2,2-dimethylpropane only has primary hydrogens? (Yes. - GS).

I know that angular strain decreases stability, and that a larger ring decreases the effects of angular strain, so in general a larger cyclic ring would be more stable but how would trans and cis play an effect? Would you still consider a larger ring to be more stable even if trans were involved in a slightly smaller ring? (Stability of cycles sharply goes up from 3- to 6-membered ring, then slightly decreases and remains virtually flat. Trans- is usually more stable than cis-, however, conformational analysis should be performed on a case-by-case basis. Except for the textbook-easy conformational analysis of cyclohexane, for larger cycles it is really convoluted and requires full-blown computational research. The good news is that overwhelming majority of useful cyclic compounds have 6-membered rings!  - GS).

For angular strain is that limited to cyclic chains? (Most often - yes. However, it may show up in noncyclic compounds if you stick too many substituents to a limited space. - GS).

Is trans generally more stable than cis? (Yes. - GS).

Is fraction distillation possible because of the different strength of attractions between molecules of alkanes? (Yes. - GS).

Overall dipole moment is zero when the dipole moment is pointing in opposite direction in equal “increments”/same electronegative value correct? so that for instance all the dipole are “pointing” outward from a central atom such as with tetrachloromethane? Is that a correct way of thinking about it? (It is close. The best way to think about it is in terms of adding vectors. - GS).

Could you explain again how you tell by looking at a drawing of a molecule whether it’s staggered or eclipsed? Thanks! (If you look along a C-C bond, and all three atoms at the second carbon are eclipsed by the respective three atoms at the first carbon, the conformation is eclipsed. Otherwise, it is staggered. - GS).

When something is more stable is it correct to assume that it also has a higher boiling point? (No. there is no relevance. - GS).

are longer chains are more stable than shorter chains? (No. - GS). so for example pentane is more stable than methane? also are branched more stable than unbranched? (Yes. - GS)

Could you interchange from the anti staggered conformation to the gauche staggered by adding energy say in terms of heat? (Yes. Even room temperature is enough for rapid interconversions. - GS). If so is there a significant noticeable difference between anti staggered and gauche compounds like does it dramatically change the chemical characteristic of the compound? (Yes. Sometimes only one of many conformation actually reacts. - GS).

What is the significance of knowing if a molecule has a anti staggered conformation or a gauche staggered? Is anti more stable? (In the anti-conformation, the distance between two substituents is larger than in the Gauche-conformation. - GS).

^^^Yes, but does that make the gauche less stable because the substituents would be very close possibly forcing other substituents to occupy their space? IS that right to think that way? (Yes, if there is no attraction between the substituents. - GS).

IS it correct to think that the eclipsed conformation is less stable meaning it has more energy because the dihedral angle is zero thus the bonds are not as far as they can possibly be?  or are those 2 things unrelated? (Eclipsed conformations always correspond to local maxima of potential energy (where the first derivative of potential energy by the dihedral angle is zero, and the second derivative is negative), which is why they are unstable. They usually have higher energy than staggered conformations (local minima where the first derivative of potential energy by the dihedral angle is zero, and the second derivative is positive), which is\also contributing to their instability. - GS).

Do newman projections specifically target the ethane bond within a compound?  (It is what you see when you look along any carbon-carbon bond, so it is not limited to ethane. - GS). Sorry, what i meant was you can only use newman projections to compare Two carbons at a time, right? (Yes, it does not describe the whole molecule except for ethane. - GS).

Is it correct to assume that aromatic hydrocarbons are strictly cyclic compounds and aliphatic hydrocarbons are “linear” (either alkane, alkene, or alkyne)? (All aromatic compounds are cyclic, but not all cyclic compounds are aromatic. Aliphatic compounds also can be cyclic. - GS).

^^^How can you differentiate between the 2 then? (The difference is historical, not chemical, and will not be important for this course. - GS).

Would you say aromatic compounds are typically stable/ more stable than aliphatic? (Yes. - GS).

Organic compounds all contain carbon does that mean that a compound with carbon can never be inorganic? (All organic compounds contain a carbon-carbon bond. Compounds with one carbon can be considered either way depending on history. - GS).

Just out of curiosity,  why are electrons more likely to show up as electron pairs and not a single electron, I think I remember that it is more stable that why, but why is this so? (If there are orbitals of same energy, electrons prefer to stay unpaired, because pairing of electrons works against their electrostatic repulsion. Most often, however, two orbitals have different energies, so both electrons are sitting on the lowest energy one. - GS).   and when would you even find a single lone electron vs. a lone electron pair? (Usually when there is an odd number of electrons, so they just cannot be paired. Also, as I noted above, a particle can have more than one unpaired electron, if it has same in energy (= degenerate) orbitals. - GS). Sorry I know this is more general chemistry but I can’t remember how to justify it.