What do the numbers listed for an element on the periodic table represent?
2 answers:
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Answer:
1. Diastereomers have different physical properties (unlike most aspects of enantiomers) and often different chemical reactivity. ... Many conformational isomers are diastereomers as well. Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction.
2. The result is a trans dibromide, as shown in the equation below
Explanation:
Diastereomers (sometimes called diastereoisomers) are a type of a stereoisomer.[1] Diasteoreomers are defined as non-mirror image non-identical stereoisomers. Hence, they occur when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.[2] When two diastereoisomers differ from each other at only one stereocenter they are epimers. Each stereocenter gives rise to two different configurations and thus typically increases the number of stereoisomers by a factor of two.
2. the addition of bromine to the trans and
cis isomers of 1,2-diphenylethene, more commonly known as trans- and cis-stilbene.
H
H
H H
trans-stilbene cis-stilbene
m.p. 122-124°C b.p. 82-84°C
density 0.970 g/mL density 1.011 g/mL
M.W. 180.25 g/mol M.W. 180.25 g/mol
In both cases, the nucleophilic double bond undergoes an electrophilic addition reaction
by the bromine reagent which proceeds via a cyclic bromonium ion. The addition of
bromine begins at one side of the double bond (either side is equally likely, but only one
option is drawn) and is followed by attack of bromide ion on the bromonium ion (again,
attack could occur at either carbon since the ion is symmetric, but only one option is
drawn). The result is a trans dibromide, as shown in the equation below:
Since the cis and trans isomers of stilbene have different geometries, it follows
that upon reaction with bromine they give rise to stereoisomeric bromonium ions and,
eventually, products that differ only by their stereochemistry.
Answer:
Explanation:
Given that:
The distillation is carried out at a pressure of 1 atm
The feed harbors 25% mole of methanol (z)
The total moles of feed is usually 100 moles
In the system, we have both methanol and water
Using the total mole balance for the distillation column.
Fz = Lx + Vy
where;
F = amount of feed
z = mole fraction of ethanol (in feed)
L = amount of liquid product out of the column
V = amount of vapor product out of the column
x = mole fraction of methanol out of the liquid
y = mole fraction of methanol out of the vapor.
SO;
(a)
If all the feed is vaporized, then the vapor will likely have the same composition as the feed.
(b)
If no vaporization of the feed takes place, then the bottoms moving out of the column contains the same composition as the feed.
(c)
If 1/3 of the feed is vaporized; then 2/3 of the feed is at the bottom.
The balance equation would be:
Replacing z = 0.25; we have:
0.75 = 2x + y
(d)
If 2/3 of the feed is vaporized;
Then:
replacing z = 0.25
0.75 = x + 2y