eretz yisrael - How does one travelling from Israel abroad (or vice versa) perform Shnayim Mikra when the parshiyot are out of sync?

Shulchan Aruch 285 codifies the obligation for each individual to read that week's parshah, the text twice and the (Aramaic) translation once.

In some years (e.g. this year, 5779) the parshiyot read in Israel and the Diaspora are one week out of sync for a number of weeks.

What does someone do when travelling from Israel to the Diaspora during this time? Would he have to read the parashah in the Diaspora a second time? Or maybe his reading the week before counts?

What does someone do when travelling from the Diaspora to Israel? Does he need to (at some point) read the parashah that he will miss hearing?

Does it make a difference if one knows that he will be returning home after his trip? Can he stick to his original schedule, despite being out of sync with where he is spending that shabbat?

product recommendation - Sefarim to learn in Elul

Which sefarim are traditionally learned in Elul*, because they have a special significance to the mood and message of the month?

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*_{Or even without a tradition, which sefarim are good to learn during this time?}

Answer

I forget who told me this, but I heard that Tomer Devorah is traditionally studied in the month of Elul.

I've been told that the Bobover Rebbe told his chassidim to learn Tomer Devorah this year, and that Rav Moshe Wolfson told his Kehilla the same a few years back.

This practice makes sense, because the first chapter of Tomer Devorah is about Hashem's 13 Middos, and how they should be taken into practice, which is a focus of the month of Elul and Yamim Noraim.

(Hebrewbooks, print Hebrew, print English)
_{These are just examples, but you can find more of all the above types at Hebrewbooks and other seforim websites; I linked to them for illustrative purposes only, not necessarily because they are the best of each type.}

inorganic chemistry - Why is BCl3 a monomer whereas AlCl3 exists as a dimer?

What makes dimerization possible in $\ce{AlCl3}$? Are there 3c-2e bonds in $\ce{Al2Cl6}$ as there are in $\ce{B2H6}$?

plagues makkos - What is considered to be "firstborn"?

This is probably a bit pedantic and beside-the-point, but here goes: in Exodus 12 (I am reading the Jewish Publication Society translation), we have:

12 For I will go through the land of Egypt in that night, and will smite all the first-born in the land of Egypt, both man and beast; and against all the gods of Egypt I will execute judgments: I am the LORD. 13 And the blood shall be to you for a token upon the houses where ye are; and when I see the blood, I will pass over you, and there shall no plague be upon you to destroy you, when I smite the land of Egypt.

Later:

29 And it came to pass at midnight, that the LORD smote all the firstborn in the land of Egypt, from the first-born of Pharaoh that sat on his throne unto the first-born of the captive that was in the dungeon; and all the first-born of cattle. 30 And Pharaoh rose up in the night, he, and all his servants, and all the Egyptians; and there was a great cry in Egypt; for there was not a house where there was not one dead.

I was wondering about what is meant to be considered "the firstborn" in this context, beyond possibly referring to male children - this detail is something I'm not sure of, since I have absolutely no idea where I picked it up. (My guess - from reading Wikipedia - is that this should be correct.) Moreover, from the second passage, this would suggest that this applies to the firstborn of each intra-family generation to me. However:

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  I'm merely making an educated guess here. Am I correct on the above points? It strikes me as slightly weird for, for instance, a firstborn elderly man to die, but this is something that I can "live" with.

  
  
  


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  Is there any indication (whether textual, or through some sort of tradition) if this applies to the firstborn of a father, or to that of a mother? Naturally in many cases, this shouldn't matter, but in others (e.g. remarriage of widowed individuals) it does.

  
  

These aren't really issues that affect the meaning of the text for me, from a "moral" angle, but I'm curious about whether or not some specifics are ever actually addressed.

organic chemistry - Inductive vs resonance effects and the acidity of phenol

A lot of people rationalize the acidity of phenol by saying that resonance is responsible for much of phenol's acidity as opposed to aliphatic alcohols.

However, this image suggests that in fact the inductive effect is responsible for a great deal of phenol's additional acidity. As we can see in the picture immediately above, it seems that the sp$^2$ carbon neighboring to the oxygen is pulling most of the weight here; that the resonance contributors with charges on carbons are minor contributors. The additional resonance contributors for phenol seem to be doing almost nothing here.

So, who's right? Resonance>inductive effect in phenol or the other way around?

EDIT: The argument I have summarized above is presented here at this website entitled "I Judge People By Their Grammar and Knowledge of Phenol"

While the chemistry in the paper was good, as The Chem Blog has noted, the authors’ lack of attention to detail was borderline disrespectful. I expected more from one of the most storied labs in synthetic organic chemistry.

[...]

It turns out that an inductive effect—not a resonance effect—is the predominant reason for the increased acidity of phenol relative to aliphatic alcohols.

[...]

For those interested, these data come from Evans’ Chem 206 lecture notes (Lecture 20, restricted access), where the point is hammered home in glorious detail. Professor Evans’ PowerPoint slides should be framed and displayed in the Smithsonian.

Addressing jerepierre's point

$\ce{Phenol + acetone~enolate \leftrightharpoons phenoxide + acetone ~enol}$

So, from the pKa values we know that the above equilibrium lies mostly to the right (according to jerepierre). Given this, we can conclude that the reactants are less stable in the acid-base sense than the products; acetone enolate is less stable than phenoxide.

Phenol is also less stable than acetone enol.

But I don't see how this contradict's the blog article. It does contradict ron's point about being unable to use the provided pKa values to compare the relative stabilities of the acids.

Answer

The acidity of $\ce{A-H}$ is a measure of where the following equilibrium lies.

$$\ce{A-H <=> A^- + H+}$$

This means that we are comparing the relative stabilities of the products and reactants ($\ce{\Delta G=-RTlnK}$).

In the present example (assuming your $\mathrm{p}K_\mathrm{a}$ for propen-2-ol is really being measured in water, note too that in water the relative concentration of this enol of acetone is ~ $10^{-8}$, how can you measure the $\mathrm{p}K_\mathrm{a}$ of something so dilute?) we are comparing the relative stability between [phenol and phenoxide] to the relative stability between [propen-2-ol and the corresponding anion]. Just because the two systems have the same difference in relative stabilities does not mean that phenol and propen-2-ol have the same stability. In other words, just because the two systems have similar $\mathrm{p}K_\mathrm{a}$'s this cannot be interpreted to mean that the additional resonance structures in phenol and phenoxide are not significant contributors to both their stability and description.

EDIT: Jerepierre's comment as worked up by Dissenter (Addressing jerepierre's point)

in his edit Dissenter wrote,

Given this, we can conclude that the reactants are less stable in the acid-base sense than the products

I agree

Dissenter further posits,

acetone enolate is less stable than phenoxide. Phenol is also less stable than acetone enol.

That's where I disagree. We know that the reactants are less stable than the products, but I don't see how we know which reactant(s) is less stable than which of the products.

Let's say the reactants are $10\,\mathrm{kcal/mol}$ (made up number) less stable than the products. Is phenol $5\,\mathrm{kcal/mol}$ less stable than phenoxide and acetone enolate $5\,\mathrm{kcal/mol}$ less stable than acetone enol? Or is it $10$ and $0$ or $0$ and $10$, or $15$ and $-5$? How can you break down the overall reactant/product difference of $10\,\mathrm{kcal/mol}$ further?

nuances - Possible ways to express remembrance and recall

How is it possible in Japanese language to express concepts of recall and remembrance?

I mean, recall is generally referred to the way we take out something from our memory which is related to people, situations and experiences of our life.

On the other hand, remembrance is the way we successfully recall not an experience, but something we learnt, something we were taught about.

Answer

@Andry covered the differences pretty well. But two other words you can use for "recall" are 思い起こす and 思い浮かべる. AFAIK they all mean pretty much the same thing, although I'm not aware of any nuances they might carry.

ions - Is it possible to have anions of metals?

I've been wondering if it is possible to have negatively charged metal ions. Most ions tend to have electron configuratons of noble gases. So then is it possible to obtain metal ions from metal atoms by changing their electron configuration to that of the next noble gas in the periodic table? (e.g. something like Be(6-))