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## How do beta lactamase inhibitors work?

Ernest Z.
Featured 6 months ago

β-Lactamase inhibitors work by blocking the activity of β-lactamase enzymes.

#### Explanation:

Some species of bacteria, such as MRSA, (Methicillin-resistant Staphylococcus aureus) develop resistance to β-lactam (penicillin-like) antibiotics by producing enzymes called β-lactamases.

The β-lactamases act by hydrolyzing the amide linkage of the β-lactam ring.

Breaking the β-lactam ring deactivates the antibiotic, and the microorganism then becomes resistant to that antibiotic.

To overcome this resistance, β-lactam antibiotics such as amoxicillin are often combined with a β-lactamase inhibitor like clavulanic acid.

(From iverson.cm.utexas.edu)

The clavulanic acid acts as a “suicide molecule”.

It binds strongly to β-lactamases and deactivates them.

The amoxicillin can then attack the bacteria that have not yet developed resistance.

## How can you learn organic chemistry nomenclature?

Meave60
Featured 4 months ago

I would recommend using note cards.

#### Explanation:

First familiarize yourself with the rules of nomenclature for organic compounds.

Then draw the structural formula of a compound (I'm assuming you have been given a list) on one side of a note card, and the name on the other side, which is a tactile learning style.

Study them, look for the application of the rules to the names of the compounds. Then quiz yourself until you have them memorized. While studying, look for patterns, such as similarities and differences, which involves both a visual learning style and critical thinking.

You can also say the names orally, which will touch on the auditory learning style, and it's much easier to remember a word if you can pronounce it (even if your pronunciation is atypical).

My technique is to go through the cards and set aside the ones that I already know. Then I study the rest and add back the ones I already know. Then I go through all the cards again, and set aside the ones I got right (hopefully there will be more). Then I study the remaining cards, and add back the cards I already know. I keep doing this until I am able to get all of the names correctly from their structural formulas, and understand why they are named that way.

This will take some investment of your time, but it is a very useful studying tool and works for many different subjects.

## How do you do a retrosynthesis of {2-[1-(4-bromophenyl)-1-phenylethoxy]ethyl}dimethylamine?

Ernest Z.
Featured 5 months ago

Here's what I get for a retrosynthesis.

#### Explanation:

You don’t identify the starting materials but, if I haven’t gone back far enough, you can probably develop appropriate retrosyntheses.

I'm starting with benzene, acetic acid, ethylene oxide. and dimethylamine.

The structure of 2-[1-(4-bromophenyl)-1-phenylethoxy]-N,N-dimethylethanamine is

(From www.chemspider.com)

The central part of the molecule is an ether. We could do a retro-Williamson ether synthesis.

Retrosynthesis of the (N,N-dimethylamino)ethyl chloride is relatively straightforward.

We can make the chloride from an alcohol, and the alcohol comes from the reaction of dimethylamine with ethylene oxide.

The remaining retrosyntheses are mostly combinations of Friedel-Crafts and Grignard reactions.

## Why is only one of the enantiomers of Ibuprofen effective?

Ernest Z.
Featured 3 months ago

Only one of the isomers is effective because it is the one that fits the receptor site on the enzyme involved in pain perception.

#### Explanation:

What ibuprofen does

Ibuprofen is works by inhibiting two enzymes called COX-1 and COX-2.

They convert arachidonic acid to prostaglandin H2 (PGH2) which, in turn, is converted by other enzymes to other prostaglandins that activate the body's response to inflammation.

How ibuprofen does it

Ibuprofen is 2-(4-isobutylphenyl)propanoic acid. Its structure is

(From scienceline.ucsb.edu)

Note the chiral centre at $\text{C2}$ of the propanoic acid.

Why only the $S$ isomer works

The ($S$)-ibuprofen has the same shape as the molecules that activate the COX enzymes to produce prostaglandins.

If we use the lock-and-key theory of enzyme action, we say that ($S$)-ibuprofen is the key that fits the lock (the receptor site) of the enzyme.

When it occupies the receptor site, it blocks access to the COX activators.

(From www.dailymail.co.uk)

The production of PGH2 ceases along with the pain and fever caused by the body's inflammatory response.

## Why do dipoles form?

Abdur R.
Featured 2 months ago

They form due to the movement and attractions of electrons in atoms and molecules.

#### Explanation:

A dipole is the separation of two opposite charges, or, in this case, partial charges.

To answer your question, we have to distinguish between the different types of dipoles. There are three different types of dipole:

• Permanent
• Oscillating
• Induced

Permanent dipoles exist in molecules with covalent bonding where one atom is more electronegative than the other. The atom which is more electronegative attracts the bonded pair of electrons to it, increasing its electron density. It thus becomes slightly negative ($\delta$ negative). On the other end of the bond, the other atom loses electron density and becomes slightly positive ($\delta$ positive). The molecule now has a permanent dipole.

Oscillating dipoles occur by chance due to the random movement of electrons in atoms. At any point, the electrons in an atom can all be concentrated on one end, reducing the electron density of the other. This causes one end of the atom to become $\delta$ positive and the other to become $\delta$ negative - the atom now has dipoles. At another time, the electrons will be concentrated on the other end, so the dipoles will shift. The dipoles will constantly be shifting due to the random movement of electrons. This is called oscillating dipoles.

Induced dipoles form when a molecule with a permanent or oscillating dipole approaches a non-polar molecule (or the other way around). As the non-polar molecule approaches the polar one, its electrons will be attracted to the $\delta$ positive end of the molecule. Thus, a dipole has been induced into the non-polar molecule.

This sort of dipole can also form when a non-polar molecule approaches an ionic molecule.

## How would you explain the halogenation of benzene?

Ernest Z.
Featured 1 week ago

The halogenation of benzene is an electrophilic aromatic substitution reaction.

#### Explanation:

Electrophilic aromatic substitution

Electrophilic aromatic substitution is a reaction in which an atom on a aromatic ring is replaced by an electrophile.

A typical halogenation reaction is

The electrophile is an ion that is generated by the catalyst.

Mechanism

Step 1. Generation of the electrophile

A Lewis acid catalyst, usually ${\text{AlBr}}_{3}$ or ${\text{FeBr}}_{3}$, reacts with the halogen to form a complex that makes the halogen more electrophilic.

Step 2. Electrophilic attack on the aromatic ring

The nucleophilic π electrons of the aromatic ring attack the electrophilic $\text{Br}$ atom .

This forms $\text{FeBr"_4^"-}$ and generates a cyclohexadienyl cation intermediate, destroying the aromaticity of the ring.

Step 3: Loss of $\text{H"^"+}$ and restoration of aromaticity

The $\text{FeBr"_4^"-}$ removes the $\text{H"^"+}$ from the ring.

This re-forms the aromatic ring, produces $\text{HBr}$, and regenerates the catalyst.

##### Questions
• 11 minutes ago · in Naming Aromatics
• An hour ago · in Dipoles
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• · 7 hours ago · in SN1 and SN2 Reactions
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