Borane Reactions - Video Tutorials & Practice Problems

Borane Reactions

Now, remember, boring itself represents a boron atom connected to three hydrogens. And when it comes to Lewis dot Structures, we know that a lot of the time elements are trying to fulfill the octet rule Bron itself though only has three valence electrons, it can only make three bonds normally. As a result of this, we're gonna say boring reactions. These reactions are driven by Bahrain's high electron deficiency. They haven't fulfilled the octet role and they're also driven by di Boras high reactivity. Remember we're using bridging hydrogens to create dibos, these structures are very unusual for us and they are highly reactive and not super stable. Now, within this section, we're gonna cover two types of reactions and they're gonna have us reacting with water and Lewis acid base reactions. One of which we know from past discussions, if you've seen my discussions on different types of acids and bases, right? So just remember when we're talking about boring reactions, it's only possible because boring itself is highly electron efficient. And if we ever covered di boring reactions, they'd be reactive as well

Reaction with H2O

Now, when it comes to the reaction with water, we're gonna say, as a result of their high reactivity, dibos readily react with liquid water. Now, gaseous Dior reacts with water to produce boric acid and hydrogen gas. So this is the only reaction that's of importance when it comes to di boring. So here we have di boring as a gas reacting with liquid water, it's gonna form boric acid which is H three bo three and we're gonna have hydrogen gas being formed as well. Once we balance this out, we'd have 162 and six, this will represent our reaction between our di boring molecule and liquid water.

Borane Reactions Example

Here in this example question, it says if the 466 kilojoules of energy is released for every mole of Dior reacting with water, how much energy would be released when 150 g of di boring is submerged in excess water? All right. So remember our balance equation is one mole of di boring gas react with six moles of water as a liquid to produce uh two moles of boric acid plus six moles of hydrogen gas. And we're just told here that the amount of energy which we're gonna say is delta H released means negative 466 kilojoules, right? So this becomes a thermal chemical question. Thermal chemical question because we're dealing with stom Mery mixed with the entropy of the reaction. So the way we set this up is we have 100 and 50 g of di boring. What we have to do first as we have to convert these grams into molds, one mole of dye boring on top grams of Dior on the bottom. So they can cancel out when you calculate the two morons. And the six hydrogens involved, you get a overall molar mass of 27.668 g grams cancel out for di boring. Now we have moles of die boring according to my balanced equation for every one mole of di boring. This is how much energy is released. OK. So here we're not doing a mole to mole comparison. We're doing a delta H to mole comparison. Everything cancels out. So what we have left at the end is negative 25 to 6.38 kilojoules. This has three sig figs, this has four sig figs. So we'd have 36 figures at the end. So negative 2520 or actually 2530 kill a jewels at the end. This is how much heat would be released from this many grams of di boring.

Lewis Acid-Base Reaction

Now recall that a Luis acid is an electron pair acceptor and a Lewis base. We'll see this is the acceptor and a Lewis Bass is an electron pair donor. Here, we're gonna say because of their high electron deficiency Boras are considered to be lois acids. So if we take a look here, we have ammonia. Molecule, nitrogen has a long pair readily available. It could share that. So it represents our lowest base boring here. Boron is making three bonds because it has three valence electrons, but it hasn't fulfilled its octet rule. So there's room for it to accept an electron pair, making it the acid Leis acid. What can happen here is nitrogen uses this lone pair and it shares it with the boron creating this new bond here. As a result of this, we're adding them together. So we call this our AUC remember the addict is just the product of our lowest base and acid reaction. If we were to determine the formal charges of the nitrogen in boron nitrogen is sharing its loan pair. So it's plus one for its formal charge boron is gaining new electrons. So it's negative one overall, the molecule will be neutral because positive and negative together. But here we're showing the formal charges on each of these atoms to be more accurate. Right. So, although boring is a new idea, Luis acid base reactions have been talked in other sections deal with acid base chemistry. So keep that in mind a boring because of its electron deficiency can act as a Luis acid and accept a lone pair from a Lewis space.

Borane Reactions Example

Here it says to draw the adduct product form from the reaction between bora and a hydroxide ion. So remember boraine is bh three hydroxide is oh minus one oxygen itself has three lone pairs. We can use one of these to connect to the boron atom. So here goes are boron still connected to its three hydrogens. And now it's making a new connection with the hydroxide ion. Oxygen still has its other two lone pairs. When oxygen makes its ideal number of bonds or just two, its formal charge is zero boron. Here is gaining additional electrons and sharing them with the oxygen. So its formal charge becomes minus one. This represents the newly created addict product between the reaction of our boring molecule and our hydroxide ion.