Consider the nucleophilic addition reaction of 2‑butanone with excess propyl magnesiumbromide, made in situ by reacting 1‑bromopropane with metallic magnesium, to make 3‑methyl‑3‑hexanol.
Reaction scheme where 2-butanone (d = 0.81 g/mL), 1-bromopropane (d=1.35 g/mL), and magnesium react to form 3-methyl-3-hexanol (d = 0.82 g/mL)
A reaction was performed in which 0.20 mL of 2‑butanone was reacted with an excess of propyl magnesiumbromide to make 0.196 g of 3‑methyl‑3‑hexanol. Calculate the theoretical yield and percent yield for this reaction.
For this question, we aren't given the chemical formulas so how would we calculate the formula molar mass when doing mol-to-gram conversions? Would we just search it up and what would we do for future questions?
Achieve Week 1 #10
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Re: Achieve Week 1 #10
You can calculate the molar mass based on the figures shown. Each "corner" of the lines represents a carbon. So you would have to add up all of the masses of C and the other elements shown in the figures to calculate the molar mass of the molecule.
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Re: Achieve Week 1 #10
A way to find the masses of 2-butanone and 3-methyl-3-hexanol without looking them up is through the given models. For 2-butanone, we can see that there is one oxygen showing and a bunch of empty intersections. For such models, an empty intersection/endpoint indicates a carbon atom with potentially some hydrogen atoms attached. For 2-butanone, there are 4 empty spaces, so there are 4 carbons there. The amount of hydrogen can be determined by looking at how many empty valence electron spots each carbon has. Carbon has a 4+ charge, meaning it has 4 empty spots in its valence shell. For example, the carbon attached to the oxygen has 2 spots taken up by the oxygen bonds and the other 2 taken up by its neighboring carbons, so there are no hydrogens needed to be attached. The carbon on the right, on the other hand, only has one bond taken up, so there needs to be 3 hydrogen attached to take up the rest of the space, and the same for the carbon on the far left. The carbon in the middle has two bonds taken up by neighboring carbons, so it has 2 hydrogens attached. So 3 + 3 + 2 hydrogens equals 8 hydrogens, making the total formula C4H8O, which when the molar mass is found (4*12 + 8 + 16) adds up to the 72 one would find when looking up the compound.
A similar process would work with 3-methyl-3-hexanol, with its empty spaces indicating 7 carbons and their available valence spots requiring 15 hydrogen, which added with the OH makes the formula C7H16O, with a molar mass of 7*12 + 16 + 16 = 116
A similar process would work with 3-methyl-3-hexanol, with its empty spaces indicating 7 carbons and their available valence spots requiring 15 hydrogen, which added with the OH makes the formula C7H16O, with a molar mass of 7*12 + 16 + 16 = 116
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Re: Achieve Week 1 #10
Thank you so much Robert! This was immensely helpful. Just to confirm, we need to assume that any empty spots will be filled by Hydrogen atoms? Thank you!
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Re: Achieve Week 1 #10
Hello, I would like to endorse the past two replies, just adding on that in the case of homework problems it is okay to google the molecular mass of more complex molecules. But it is great practice to begin understanding how to read the drawn molecules. In the case of drawn organic molecules you assume that every "point" which is a carbon atom, is fully substituted, which means that it has four bonds coming off it. If four bonds are not shown the difference between the bonds shown and 4 is the number of hydrogens bound to the carbon atom.
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Re: Achieve Week 1 #10
You can use the skeletal formulas given to determine the chemical formulas of the compounds. Each edge is one carbon and one carbon can only have 4 bonds. Hydrogens are not shown on the skeletal formula.
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Re: Achieve Week 1 #10
The pictures (skeletal formulas) represent the chemical formulas of the compounds. Each point is a carbon and hydrogen atoms are not shown. Robert's answer is very helpful in terms of the detailed version of how to figure out the ratios. Definitely check his out first!
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