How do you assign octane ratings? (It is the percentage of isooctane in its mixture with n-heptane that has same resistance to detonation as the tested fuel. - GS).  

What is the difference between CH3 and alkyl? (Methyl is an example of alkyl - GS).

Would you mind explaining why ethanol for gasoline is so effective at functioning as a “fuel”? (Ethanol increases resistance of fuel to premature ignition (increases octane rating) by intercepting free radicals, but decreases the energy content of fuel (mileage) - GS).

The flammability is due to its ability to oxidize in addition to its high energy, right? so what makes a molecule more capable of oxidizing?  (This is a good factor, but it is also important how well the compound mixes with oxygen, and how well a free-radical chain reaction sustains. - 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).

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).

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).

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).

How do we know where the molecule will split when it undergoes cracking? (Preferably - to form the most stable free radical. - GS).