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Mark asks…

Other than THF and diethyl ether, what could one use as a solvent for a Grignard? Why are these suitable?

So THF and diethyl ether are both slightly polar but why is that important? I need to know other solvents that could be used for Grignard and what would make a bad solvent and why? I’m guessing a nonpolar solvent would make a bad solvent, or maybe something very polar and thus easier for water to dissolve in? Help!

weight loss cardiff answers:

You’re partly right, a nonpolar solvent wouldn’t work. The Grignard reagent is polar and would not be very soluble in a nonpolar solvent.

To see what kind of polar solvents work best, first remember that the Grignard reaction proceeds through an SN2 mechanism. Your Grignard reagent has a dipole moment, (δ−)R−(δ+)MgBr. That partial negative charge turns the R group from a bad nucleophile to a strong nucleophile, which SN2 needs. But it also makes it a strong base. Because of that, we have to be careful with our solvent. If the solvent we use is even a little bit acidic, some of the Grignard reagent will be diverted into an acid-base side reaction with the solvent, instead of the desired nucleophilic substitution.

So, to enhance a reagent’s nucleophilicity for SN2, we need to use a solvent that is polar, but cannot act as an acid. THF and Et2O fit this description; they have dipole moments but don’t contain acidic hydrogens. Since they won’t give up H+ (a proton), we call this type of solvent a “polar aprotic” solvent.

Grignard reagents in particular are highly reactive toward many polar aprotic solvents, further reducing the number of solvents that will work. For instance, your Grignard reagent would attack an acetone solvent, (CH3)2C=O, since it contains a ketone. You’re basically forced to use an ether solvent with Grignard. So, another ether solvent you might use for Grignard is dibutyl ether.

Short, cram night before the test version:
1) Grignard is SN2
2) polar aprotic solvents favor SN2
3) Grignard side-reacts with solvents other than ethers

Laura asks…

Is benzoic acid more soluble in water or diethyl ether?

When both water and diethyl ether were added to benzoic acid, which layer(ie the organic or aqueous layer) can the benzoic acid can be found.
i am also curious that if benzoic acid is more soluble in diethyl ether, is it due to the 6 carbon chain of the benzoic acid?
C6H5coo- soluble in water?

weight loss cardiff answers:

Benzoic acid is more soluble in diethyl ether than water.

So benzoic acid would be in the organic layer.

Bear in mind that ether is less dense than water, so the extract would be on top.

Benzoic acid is more soluble in ether because the benzene ring is nonpolar, aye.

Benzoate salts are water soluble, though, because water is better able to stabilize the negative charge on the oxygen.

Maria asks…

what is the difference Between Ethyl Ether and Diethyl Ether?

i was in chemistry the other day and we were talking about Ether
and i was curious what’s the difference between the two.

weight loss cardiff answers:

Nothing, they represent the same compound. Diethyl ether is the correct IUPAC name for the compound composed of an oxygen attached to two ethyl groups. Ethyl ether is a common name for the same compound. Not technically correct, but widely understood to mean diethyl ether.

Note that sometimes, this compound is also refered to simply as “ether”.

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Michael asks…

Help with determining concentration of diethyl ether?

2.5 L of diethyl ether was spilt on the floor of a lab with the volume of 486m3. The STEL (short term exposure limit), which is the maximum permissable concentration in air allowed of a substance in a workplace is 1520 mg/m3. The density of diethyl ether is 255. Assuming all of the ether will evaporate rapidly into the air. Will the concentration of diethyl ether in the air exceed the STEL?

weight loss cardiff answers:

The density of diethyl ether at 20 deg C is 0.7135 g/mL. (Your value of 255 – unknown units – is wrong).
2.5 L x 1000 mL/L x 0.7135 g/mL x 1000 mg/g = 1,784,000 mg
1,784,000 mg / 486 m^3 = 3670 mg/m^3
3670 mg/m^3 exceeds 1520 mg/m^3

John asks…

what is the force between hexane and diethyl ether?

Is it dipole-induced dipole because diethyl ether is polar? Hexane isn’t polar right?

weight loss cardiff answers:

There are only london dispersion forces between the two chemicals, because hexane is nonpolar, and cannot have any other intermolecular attractions

Richard asks…

How do you extract Diethyl ether from starter fluid?

I heard that it can simply be done with water but petroleum distillates do not dissolve in water and the distillates stay mixed with the ether but I dont know.

weight loss cardiff answers:

In short, not really. The only way to effectively separate petroleum distillates from diethyl ether in starter fluid is by fractional distillation. This requires appropriate equipment and training in relevant lab procedures, can be EXTREMELY dangerous, and is outside of the skillset of most people.

Some websites and experience reports mention a “water extraction” procedure that involves shaking a mixture of distilled water and starter fluid.

The so-called “water extraction” method is simplistic and ineffective, since petroleum distillates and water are not miscible (petroleum distillates do not dissolve in water), and the distillates stay mixed with the ether, because of their common chemical nature. In fact, if the components in the water-insoluble fraction were to separate, which is highly unlikely, the density of ether would put it at the bottom, closest to the water, at the water:non-polar interface, making it very difficult to isolate. Because ether is slightly soluble in distilled water, the volume of the ether in the water-insoluble fraction may actually be reduced by repeated shaking and separating.

Ether is slightly soluble in distilled water and heptane is insoluble. Hence, if one were to try to clean up starting fluid via repeatedly shaking with distilled H2O and then separating the layers, you not only don’t end up with very good ET2O, but you are actually reducing the amount of ether that you have.

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Mark asks…

Chlorocyclohexane + Mg in diethyl ether can be what kind of reaction?

We’ve been studying alkanes alkenes and alkynes but so far I haven’t seen a reaction with Mg and diethyl ether. What kind of alkane reaction can that be?

weight loss cardiff answers:

This is a Grignard reaction to form the Grignard reagent cyclohexylmagnesium chloride. Grignard reactions are reactions between halogenoalkanes/arenes and magnesium to form Grignard reagents which are nucleophiles and are used in synthesis to add alkyl/aryl groups to a compound.

Ruth asks…

What is the heat required to vaporize 80.0 g of liquid diethyl ether, (C2H5)2O, at its boiling point?

The ΔH° of vaporization of diethyl ether is 26.0 kJ/mol. Use a molar mass with at least as many significant figures as the data given.

weight loss cardiff answers:

Know: MM=74.12 g/mol (C2H5)O2
want: x kJ

step 1: start with g, go to mol, go to kJ
step 2: check ans

80 g x(mol/74.12 g) x(26 kJ/mol)=28.1 kJ

Nancy asks…

What is the density of Diethyl Ether?

Diethyl ether, (C2H5)2O, vaporizes easily at room temperature. If the vapor exerts a pressure of 233mm Hg in a flask at 25’C, what is the density of the vapor?

weight loss cardiff answers:

Density = mass/volume

Since mass is the number of moles (n) * molar mass (M), density = nM/V

According to the ideal gas law, PV = nRT. Therefore, n = PV/RT

Plug that in for n in the density equation to get

density = PVM/(RTV)

The V’s cancel, so the final equation for density is

density = PM/RT

Convert the vapor pressure of 233 mmHg to 1 atm (1 atm = 760 mmHg), convert the temperature from Celsius to Kelvin (Celcius + 273 = Kelvin), and use R = 0.0821 L*atm / (mol*K). Find molar mass of diethyl ether

C = 12.01 x 4 = 48.04g
H = 1.01 x 10 = 10.10g
O = 16.00 x 1 = 16.00g

molar mass M = 74.14g/mol

density = (233 mmHg * 1 atm / 760 mmHg) * 74.14g/mol / (298 K * 0.0821) = 0.93 g/L

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Lizzie asks…

Why does 1-butanol has a higher boiling point than diethyl ether?

Why does 1-butanol has a higher boiling point than diethyl ether? Which compound would you expect to be more soluble in water? Why?

weight loss cardiff answers:

1-butanol

OH
|
C-C-C-C

diethyl ether

CH3-CH2-O-CH2-CH3

a) * I (think) the answer to this lies in the hydrogen bonds from the OH group to other OH groups. It has been a while since I’ve had Organic Chem.
B) butanol.
C) the terminal OH group makes the ends more polar and more soluable in water

Carol asks…

Why are amines charged in a pH = 2 solution of diethyl ether and water?

Why are amines charged in a pH = 2 solution of diethyl ether and water, whereas alcohols and carboxylic acids are neutral? What determines if a substance will become charged or not in low or high pH? My organic chemistry book does not explain it well.

weight loss cardiff answers:

Amines, R-NH2, will in acid media pick up a proton to become R-NH3+

Acids, however, cannot absorb an H+; they release them. So in an acid medium, unless the acid in question is stronger it will not dissociate [much – use Ka if you need to get exact].

Alcohols do not generally pick up or discharge ions.

THis should have been covered in intro chem, and is assumed as background info in orgo

Helen asks…

Why is methanol more soluble in water than diethyl ether?

Is it just because the carbon chain is longer in diethyl ether?or are there other factors too?

weight loss cardiff answers:

Theres a saying that goes “like dissolves like”.

Water is a polar molecule, meaning it will dissolve other polar molecules more easily. By looking at the structure of each you can see that methanol is more polar than diethyl ether, largely because of OH group of methanol, in which the hydrogen atom is more easily detached.

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